global-helpers.js

(function(__global) {
  var loader = $__System;
  var hasOwnProperty = Object.prototype.hasOwnProperty;
  var indexOf = Array.prototype.indexOf || function(item) {
    for (var i = 0, l = this.length; i < l; i++)
      if (this[i] === item)
        return i;
    return -1;
  }

  function readMemberExpression(p, value) {
    var pParts = p.split('.');
    while (pParts.length)
      value = value[pParts.shift()];
    return value;
  }

  function getGlobalValue(exports) {
    if (typeof exports == 'string')
      return readMemberExpression(exports, __global);

    if (!(exports instanceof Array))
      throw new Error('Global exports must be a string or array.');

    var globalValue = {};
    var first = true;
    for (var i = 0; i < exports.length; i++) {
      var val = readMemberExpression(exports[i], __global);
      if (first) {
        globalValue['default'] = val;
        first = false;
      }
      globalValue[exports[i].split('.').pop()] = val;
    }
    return globalValue;
  }

  // bare minimum ignores
  var ignoredGlobalProps = ['_g', 'sessionStorage', 'localStorage', 'clipboardData', 'frames', 'frameElement', 'external', 
      'mozAnimationStartTime', 'webkitStorageInfo', 'webkitIndexedDB', 'mozInnerScreenY', 'mozInnerScreenX'];

  var globalSnapshot;

  function forEachGlobal(callback) {
    if (Object.keys)
      Object.keys(__global).forEach(callback);
    else
      for (var g in __global) {
        if (!hasOwnProperty.call(__global, g))
          continue;
        callback(g);
      }
  }

  function forEachGlobalValue(callback) {
    forEachGlobal(function(globalName) {
      if (indexOf.call(ignoredGlobalProps, globalName) != -1)
        return;
      try {
        var value = __global[globalName];
      }
      catch (e) {
        ignoredGlobalProps.push(globalName);
      }
      callback(globalName, value);
    });
  }

  loader.set('@@global-helpers', loader.newModule({
    prepareGlobal: function(moduleName, exports, globals) {
      // disable module detection
      var curDefine = __global.define;
      __global.define = undefined;

      // set globals
      var oldGlobals;
      if (globals) {
        oldGlobals = {};
        for (var g in globals) {
          oldGlobals[g] = __global[g];
          __global[g] = globals[g];
        }
      }

      // store a complete copy of the global object in order to detect changes
      if (!exports) {
        globalSnapshot = {};

        forEachGlobalValue(function(name, value) {
          globalSnapshot[name] = value;
        });
      }

      // return function to retrieve global
      return function() {
        var globalValue;

        if (exports) {
          globalValue = getGlobalValue(exports);
        }
        else {
          globalValue = {};
          var singleGlobal;
          var multipleExports;

          forEachGlobalValue(function(name, value) {
            if (globalSnapshot[name] === value)
              return;
            if (typeof value == 'undefined')
              return;
            globalValue[name] = value;

            if (typeof singleGlobal != 'undefined') {
              if (!multipleExports && singleGlobal !== value)
                multipleExports = true;
            }
            else {
              singleGlobal = value;
            }
          });
          globalValue = multipleExports ? globalValue : singleGlobal;
        }

        // revert globals
        if (oldGlobals) {
          for (var g in oldGlobals)
            __global[g] = oldGlobals[g];
        }
        __global.define = curDefine;

        return globalValue;
      };
    }
  }));

})(typeof self != 'undefined' ? self : global);