src/URIUtils.js

/**
 * @license
 * Copyright 2017 The Emscripten Authors
 * SPDX-License-Identifier: MIT
 */

function hasPrefix(str, prefix) {
  return String.prototype.startsWith ?
      str.startsWith(prefix) :
      str.indexOf(prefix) === 0;
}

// Prefix of data URIs emitted by SINGLE_FILE and related options.
var dataURIPrefix = 'data:application/octet-stream;base64,';

// Indicates whether filename is a base64 data URI.
function isDataURI(filename) {
  return hasPrefix(filename, dataURIPrefix);
}

var fileURIPrefix = "file://";

// Indicates whether filename is delivered via file protocol (as opposed to http/https)
function isFileURI(filename) {
  return hasPrefix(filename, fileURIPrefix);
}