js/util/query-args.js

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/*
Provides a simple way to get values from the query string if they're present
and use a default value if not. Not strictly a "WebGL" utility, but I use it
frequently enough for debugging that I wanted to include it here.

Example:
For the URL http://example.com/index.html?particleCount=1000

QueryArgs.getInt("particleCount", 100); // URL overrides, returns 1000
QueryArgs.getInt("particleSize", 10); // Not in URL, returns default of 10
*/

let urlArgs = null;
window.onhashchange = function() {
  // Force re-parsing on next access
  urlArgs = null;
};

function ensureArgsCached() {
  if (!urlArgs) {
    urlArgs = {};
    let query = window.location.search.substring(1) || window.location.hash.substring(1);
    let vars = query.split('&');
    for (let i = 0; i < vars.length; i++) {
      let pair = vars[i].split('=');
      urlArgs[pair[0].toLowerCase()] = decodeURIComponent(pair[1]);
    }
  }
}

export class QueryArgs {
  static getString(name, defaultValue) {
    ensureArgsCached();
    let lcaseName = name.toLowerCase();
    if (lcaseName in urlArgs) {
      return urlArgs[lcaseName];
    }
    return defaultValue;
  }

  static getInt(name, defaultValue) {
    ensureArgsCached();
    let lcaseName = name.toLowerCase();
    if (lcaseName in urlArgs) {
      return parseInt(urlArgs[lcaseName], 10);
    }
    return defaultValue;
  }

  static getFloat(name, defaultValue) {
    ensureArgsCached();
    let lcaseName = name.toLowerCase();
    if (lcaseName in urlArgs) {
      return parseFloat(urlArgs[lcaseName]);
    }
    return defaultValue;
  }

  static getBool(name, defaultValue) {
    ensureArgsCached();
    let lcaseName = name.toLowerCase();
    if (lcaseName in urlArgs) {
      return parseInt(urlArgs[lcaseName], 10) != 0;
    }
    return defaultValue;
  }
}