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            "web-features:snapshot:ecmascript-1"
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            "standard_track": true,
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          "tags": [
            "web-features:snapshot:ecmascript-1"
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          "support": {
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            "samsunginternet_android": "mirror",
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          "status": {
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            "standard_track": true,
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              "version_added": "5"
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            "safari_ios": "mirror",
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          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
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          "description": "<code>do...while</code>",
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/do...while",
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          "support": {
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            "web-features:snapshot:ecmascript-1"
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            "standard_track": true,
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          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-scripts-and-modules.html#sec-exports",
          "tags": [
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          "support": {
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              "version_added": "38"
            },
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              "version_added": "12"
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              "version_added": "13",
              "notes": "Before Firefox 51, using the <code>for...of</code> loop construct with the <code>const</code> keyword threw a <code>SyntaxError</code> (\"missing = in const declaration\")."
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              "version_added": "7"
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            "samsunginternet_android": "mirror",
            "webview_android": "mirror",
            "webview_ios": "mirror"
          },
          "status": {
            "experimental": false,
            "standard_track": true,
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            "description": "async iterators",
            "tags": [
              "web-features:snapshot:ecmascript-2018"
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            "support": {
              "chrome": {
                "version_added": "63"
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.0"
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              "edge": {
                "version_added": "12"
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              "firefox": {
                "version_added": "57"
              },
              "firefox_android": "mirror",
              "ie": {
                "version_added": false
              },
              "nodejs": {
                "version_added": "10.0.0"
              },
              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": "7"
              },
              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
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              "standard_track": true,
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              "chrome": {
                "version_added": "51"
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              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.0"
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              "edge": {
                "version_added": "14"
              },
              "firefox": {
                "version_added": "53"
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              "firefox_android": "mirror",
              "ie": {
                "version_added": false
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              "nodejs": {
                "version_added": "6.5.0"
              },
              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": "7"
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              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
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          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function",
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            "oculus": "mirror",
            "opera": {
              "version_added": "3"
            },
            "opera_android": {
              "version_added": "10.1"
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              "version_added": "1"
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            "samsunginternet_android": "mirror",
            "webview_android": "mirror",
            "webview_ios": "mirror"
          },
          "status": {
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            "description": "Trailing comma in parameters",
            "tags": [
              "web-features:functions"
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            "support": {
              "chrome": {
                "version_added": "58"
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.0"
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              "edge": {
                "version_added": "14"
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              "firefox": {
                "version_added": "52"
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              "firefox_android": "mirror",
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                "version_added": false
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              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
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              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
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          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function*",
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          "tags": [
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              "version_added": "39"
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              "version_added": "13"
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          },
          "status": {
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            "standard_track": true,
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            "description": "<code>IteratorResult</code> object instead of throwing",
            "tags": [
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              "web-features:generators"
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              "chrome": {
                "version_added": "49"
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              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.0"
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              "edge": {
                "version_added": "13"
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              "firefox": {
                "version_added": "29"
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              "firefox_android": "mirror",
              "ie": {
                "version_added": false
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              "nodejs": {
                "version_added": "6.0.0"
              },
              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": "10"
              },
              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
              "experimental": false,
              "standard_track": true,
              "deprecated": false
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          }
        },
        "not_constructable_with_new": {
          "__compat": {
            "description": "Not constructable with <code>new</code> (ES2016)",
            "tags": [
              "web-features:snapshot:ecmascript-2016",
              "web-features:generators"
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            "support": {
              "chrome": {
                "version_added": "50"
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.0"
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              "edge": {
                "version_added": "13"
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              "firefox": {
                "version_added": "43"
              },
              "firefox_android": "mirror",
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              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": "10"
              },
              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
              "experimental": false,
              "standard_track": true,
              "deprecated": false
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          }
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        "trailing_comma_in_parameters": {
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            "description": "Trailing comma in parameters",
            "tags": [
              "web-features:generators"
            ],
            "support": {
              "chrome": {
                "version_added": "58"
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.0"
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              "edge": {
                "version_added": "14"
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              "firefox": {
                "version_added": "52"
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                "version_added": false
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              "nodejs": {
                "version_added": "8.0.0"
              },
              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": "10"
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              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
              "experimental": false,
              "standard_track": true,
              "deprecated": false
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          }
        }
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          "description": "<code>if...else</code>",
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/if...else",
          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-if-statement",
          "tags": [
            "web-features:snapshot:ecmascript-1"
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          "support": {
            "chrome": {
              "version_added": "1"
            },
            "chrome_android": "mirror",
            "deno": {
              "version_added": "1.0"
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            "edge": {
              "version_added": "12"
            },
            "firefox": {
              "version_added": "1"
            },
            "firefox_android": "mirror",
            "ie": {
              "version_added": "3"
            },
            "nodejs": {
              "version_added": "0.10.0"
            },
            "oculus": "mirror",
            "opera": {
              "version_added": "3"
            },
            "opera_android": {
              "version_added": "10.1"
            },
            "safari": {
              "version_added": "1"
            },
            "safari_ios": "mirror",
            "samsunginternet_android": "mirror",
            "webview_android": "mirror",
            "webview_ios": "mirror"
          },
          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
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        }
      },
      "import": {
        "__compat": {
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/import",
          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-scripts-and-modules.html#sec-imports",
          "tags": [
            "web-features:js-modules"
          ],
          "support": {
            "chrome": {
              "version_added": "61"
            },
            "chrome_android": "mirror",
            "deno": {
              "version_added": "1.0"
            },
            "edge": {
              "version_added": "16"
            },
            "firefox": {
              "version_added": "60"
            },
            "firefox_android": "mirror",
            "ie": {
              "version_added": false
            },
            "nodejs": [
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                "version_added": "13.2.0",
                "notes": "Modules must either have a filename ending in <code>.mjs</code>, or the nearest parent <code>package.json</code> file must contain <code>\"type\": \"module\"</code>. See Node's <a href='https://nodejs.org/api/esm.html#esm_enabling'>ECMAScript Modules documentation</a> for more details."
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            "oculus": "mirror",
            "opera": "mirror",
            "opera_android": "mirror",
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              "version_added": "10.1"
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            "safari_ios": "mirror",
            "samsunginternet_android": "mirror",
            "webview_android": "mirror",
            "webview_ios": "mirror"
          },
          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
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        "worker_support": {
          "__compat": {
            "description": "Available in workers",
            "tags": [
              "web-features:js-modules-workers"
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            "support": {
              "chrome": {
                "version_added": "80"
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.0"
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              "edge": "mirror",
              "firefox": {
                "version_added": "114"
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              "firefox_android": "mirror",
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                "version_added": false
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              "nodejs": {
                "version_added": false
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              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": "15"
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              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
              "experimental": false,
              "standard_track": true,
              "deprecated": false
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          }
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            "description": "Import attributes with <code>assert</code> syntax (formerly import assertions)",
            "support": {
              "chrome": {
                "version_added": "91",
                "version_removed": "126"
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.17"
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              "edge": "mirror",
              "firefox": {
                "version_added": false
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              "firefox_android": "mirror",
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              "oculus": "mirror",
              "opera": {
                "version_added": false
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              "opera_android": {
                "version_added": false
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              "safari": {
                "version_added": false
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              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
              "experimental": false,
              "standard_track": false,
              "deprecated": true
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              "description": "<code>assert {type: 'css'}</code>",
              "support": {
                "chrome": {
                  "version_added": "93",
                  "version_removed": "126"
                },
                "chrome_android": "mirror",
                "deno": {
                  "version_added": false
                },
                "edge": "mirror",
                "firefox": {
                  "version_added": false,
                  "impl_url": "https://bugzil.la/1720570"
                },
                "firefox_android": "mirror",
                "ie": {
                  "version_added": false
                },
                "nodejs": {
                  "version_added": false
                },
                "oculus": "mirror",
                "opera": {
                  "version_added": false
                },
                "opera_android": {
                  "version_added": false
                },
                "safari": {
                  "version_added": false,
                  "impl_url": "https://webkit.org/b/227967"
                },
                "safari_ios": "mirror",
                "samsunginternet_android": "mirror",
                "webview_android": "mirror",
                "webview_ios": "mirror"
              },
              "status": {
                "experimental": false,
                "standard_track": false,
                "deprecated": true
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            }
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              "description": "<code>assert {type: 'json'}</code>",
              "support": {
                "chrome": {
                  "version_added": "91",
                  "version_removed": "126"
                },
                "chrome_android": "mirror",
                "deno": {
                  "version_added": "1.17"
                },
                "edge": "mirror",
                "firefox": {
                  "version_added": false
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                "firefox_android": "mirror",
                "ie": {
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                "nodejs": [
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                    "version_removed": "22.0.0"
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                  {
                    "version_added": "16.15.0",
                    "version_removed": "17.0.0"
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                ],
                "oculus": "mirror",
                "opera": {
                  "version_added": false
                },
                "opera_android": {
                  "version_added": false
                },
                "safari": {
                  "version_added": false
                },
                "safari_ios": "mirror",
                "samsunginternet_android": "mirror",
                "webview_android": "mirror",
                "webview_ios": "mirror"
              },
              "status": {
                "experimental": false,
                "standard_track": false,
                "deprecated": true
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            }
          }
        },
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          "__compat": {
            "description": "Import attributes (<code>with</code> syntax)",
            "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/import/with",
            "spec_url": "https://tc39.es/proposal-import-attributes/#prod-WithClause",
            "support": {
              "chrome": {
                "version_added": "123"
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.37"
              },
              "edge": "mirror",
              "firefox": {
                "version_added": false,
                "impl_url": "https://bugzil.la/1736059"
              },
              "firefox_android": "mirror",
              "ie": {
                "version_added": false
              },
              "nodejs": [
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                  "version_added": "20.10.0"
                },
                {
                  "version_added": "18.20.0",
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              ],
              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": "17.2"
              },
              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
              "experimental": false,
              "standard_track": true,
              "deprecated": false
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          },
          "type_css": {
            "__compat": {
              "description": "<code>with {type: 'css'}</code>",
              "tags": [
                "web-features:css-modules"
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              "support": {
                "chrome": {
                  "version_added": "123"
                },
                "chrome_android": "mirror",
                "deno": {
                  "version_added": false
                },
                "edge": "mirror",
                "firefox": {
                  "version_added": false
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                "firefox_android": "mirror",
                "ie": {
                  "version_added": false
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                "nodejs": {
                  "version_added": false
                },
                "oculus": "mirror",
                "opera": "mirror",
                "opera_android": "mirror",
                "safari": {
                  "version_added": false
                },
                "safari_ios": "mirror",
                "samsunginternet_android": "mirror",
                "webview_android": "mirror",
                "webview_ios": "mirror"
              },
              "status": {
                "experimental": true,
                "standard_track": true,
                "deprecated": false
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            }
          },
          "type_json": {
            "__compat": {
              "description": "<code>with {type: 'json'}</code>",
              "tags": [
                "web-features:json-modules"
              ],
              "support": {
                "chrome": {
                  "version_added": "123"
                },
                "chrome_android": "mirror",
                "deno": {
                  "version_added": "1.37"
                },
                "edge": "mirror",
                "firefox": {
                  "version_added": false,
                  "impl_url": "https://bugzil.la/1736059"
                },
                "firefox_android": "mirror",
                "ie": {
                  "version_added": false
                },
                "nodejs": [
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                    "version_added": "20.10.0"
                  },
                  {
                    "version_added": "18.20.0",
                    "version_removed": "19.0.0"
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                ],
                "oculus": "mirror",
                "opera": "mirror",
                "opera_android": "mirror",
                "safari": {
                  "version_added": "17.2"
                },
                "safari_ios": "mirror",
                "samsunginternet_android": "mirror",
                "webview_android": "mirror",
                "webview_ios": "mirror"
              },
              "status": {
                "experimental": false,
                "standard_track": true,
                "deprecated": false
              }
            }
          }
        },
        "service_worker_support": {
          "__compat": {
            "description": "Available in service workers",
            "tags": [
              "web-features:js-modules-service-workers"
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            "support": {
              "chrome": {
                "version_added": "91"
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": false
              },
              "edge": "mirror",
              "firefox": {
                "version_added": false,
                "impl_url": "https://bugzil.la/1360870"
              },
              "firefox_android": "mirror",
              "ie": {
                "version_added": false
              },
              "nodejs": {
                "version_added": false
              },
              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": "15"
              },
              "safari_ios": "mirror",
              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
              "experimental": false,
              "standard_track": true,
              "deprecated": false
            }
          }
        },
        "worklet_support": {
          "__compat": {
            "description": "Available in worklets",
            "support": {
              "chrome": {
                "version_added": false
              },
              "chrome_android": "mirror",
              "deno": {
                "version_added": false
              },
              "edge": "mirror",
              "firefox": {
                "version_added": "114"
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              "firefox_android": "mirror",
              "ie": {
                "version_added": false
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              "nodejs": {
                "version_added": false
              },
              "oculus": "mirror",
              "opera": "mirror",
              "opera_android": "mirror",
              "safari": {
                "version_added": false
              },
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              "samsunginternet_android": "mirror",
              "webview_android": "mirror",
              "webview_ios": "mirror"
            },
            "status": {
              "experimental": false,
              "standard_track": true,
              "deprecated": false
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          }
        }
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        "__compat": {
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/label",
          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-labelled-statements",
          "tags": [
            "web-features:snapshot:ecmascript-3"
          ],
          "support": {
            "chrome": {
              "version_added": "1"
            },
            "chrome_android": "mirror",
            "deno": {
              "version_added": "1.0"
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            "edge": {
              "version_added": "12"
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            "firefox": {
              "version_added": "1"
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            "firefox_android": "mirror",
            "ie": {
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            "opera": {
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            "opera_android": {
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            "safari": {
              "version_added": "1"
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            "safari_ios": "mirror",
            "samsunginternet_android": "mirror",
            "webview_android": "mirror",
            "webview_ios": "mirror"
          },
          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
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        }
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        "__compat": {
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/let",
          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-let-and-const-declarations",
          "tags": [
            "web-features:snapshot:ecmascript-2015"
          ],
          "support": {
            "chrome": [
              {
                "version_added": "49"
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              {
                "version_added": "41",
                "version_removed": "49",
                "partial_implementation": true,
                "notes": "<a href='https://developer.mozilla.org/docs/Web/JavaScript/Reference/Strict_mode'>Strict mode</a> is required."
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            "chrome_android": "mirror",
            "deno": {
              "version_added": "1.0"
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            "edge": [
              {
                "version_added": "14"
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              {
                "version_added": "12",
                "version_removed": "14",
                "partial_implementation": true,
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              "version_added": "44",
              "notes": [
                "Before Firefox 44, <code>let</code> is only available to code blocks in HTML wrapped in a <code>&lt;script type=\"application/javascript;version=1.7\"&gt;</code> block (or higher version) and has different semantics (e.g. no temporal dead zone).",
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                "Firefox 54 adds support of <code>let</code> in workers."
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              "version_added": "11",
              "partial_implementation": true,
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            "opera_android": {
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            "safari": {
              "version_added": "10"
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            "safari_ios": "mirror",
            "samsunginternet_android": "mirror",
            "webview_android": "mirror",
            "webview_ios": "mirror"
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          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
          }
        }
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        "__compat": {
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/return",
          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-return-statement",
          "tags": [
            "web-features:snapshot:ecmascript-1"
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          "support": {
            "chrome": {
              "version_added": "1"
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            "chrome_android": "mirror",
            "deno": {
              "version_added": "1.0"
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            "edge": {
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              "version_added": "1"
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            "firefox_android": "mirror",
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            "nodejs": {
              "version_added": "0.10.0"
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            "oculus": "mirror",
            "opera": {
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            "opera_android": {
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            "safari": {
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            "safari_ios": "mirror",
            "samsunginternet_android": "mirror",
            "webview_android": "mirror",
            "webview_ios": "mirror"
          },
          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
          }
        }
      },
      "switch": {
        "__compat": {
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/switch",
          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-switch-statement",
          "support": {
            "chrome": {
              "version_added": "1"
            },
            "chrome_android": "mirror",
            "deno": {
              "version_added": "1.0"
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            "edge": {
              "version_added": "12"
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            "firefox": {
              "version_added": "1"
            },
            "firefox_android": "mirror",
            "ie": {
              "version_added": "4"
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            "nodejs": {
              "version_added": "0.10.0"
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            "oculus": "mirror",
            "opera": {
              "version_added": "4"
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            "opera_android": {
              "version_added": "10.1"
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            "safari": {
              "version_added": "1"
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            "safari_ios": "mirror",
            "samsunginternet_android": "mirror",
            "webview_android": "mirror",
            "webview_ios": "mirror"
          },
          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
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        }
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      "throw": {
        "__compat": {
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/throw",
          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-throw-statement",
          "tags": [
            "web-features:snapshot:ecmascript-3"
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          "support": {
            "chrome": {
              "version_added": "1"
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            "chrome_android": "mirror",
            "deno": {
              "version_added": "1.0"
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            "edge": {
              "version_added": "12"
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            "firefox": {
              "version_added": "1"
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              "version_added": "5"
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            "opera_android": {
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            "safari": {
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            "webview_android": "mirror",
            "webview_ios": "mirror"
          },
          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
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        }
      },
      "try_catch": {
        "__compat": {
          "description": "<code>try...catch</code>",
          "mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/try...catch",
          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-try-statement",
          "tags": [
            "web-features:snapshot:ecmascript-3"
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          "support": {
            "chrome": {
              "version_added": "1"
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            "chrome_android": "mirror",
            "deno": {
              "version_added": "1.0"
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            "edge": {
              "version_added": "12"
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            "firefox": {
              "version_added": "1"
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            "firefox_android": "mirror",
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            "nodejs": {
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            "opera_android": {
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            "safari": {
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            "safari_ios": "mirror",
            "samsunginternet_android": "mirror",
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            "webview_ios": "mirror"
          },
          "status": {
            "experimental": false,
            "standard_track": true,
            "deprecated": false
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        },
        "optional_catch_binding": {
          "__compat": {
            "description": "Optional catch binding",
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              "chrome": {
                "version_added": "66"
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              "chrome_android": "mirror",
              "deno": {
                "version_added": "1.0"
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              "oculus": "mirror",
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              "safari_ios": "mirror",
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            "status": {
              "experimental": false,
              "standard_track": true,
              "deprecated": false
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          }
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      "var": {
        "__compat": {
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          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-variable-statement",
          "tags": [
            "web-features:snapshot:ecmascript-1"
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          "support": {
            "chrome": {
              "version_added": "1"
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            "chrome_android": "mirror",
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            "standard_track": true,
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            "standard_track": true,
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          "spec_url": "https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-with-statement",
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            "webview_android": "mirror",
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            "standard_track": true,
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}