systemjs/lib/global.js

/*
  SystemJS Global Format

  Supports
    metadata.deps
    metadata.init
    metadata.exports

  Also detects writes to the global object avoiding global collisions.
  See the SystemJS readme global support section for further information.
*/
(function() {

  hookConstructor(function(constructor) {
    return function() {
      var loader = this;
      constructor.call(loader);

      var hasOwnProperty = __global.hasOwnProperty;

      var curGlobalObj;
      var ignoredGlobalProps = ['indexedDB', 'sessionStorage', 'localStorage',
          'clipboardData', 'frames', 'webkitStorageInfo', 'toolbar', 'statusbar',
          'scrollbars', 'personalbar', 'menubar', 'locationbar', 'webkitIndexedDB',
          'screenTop', 'screenLeft'];

      loader.set('@@global-helpers', loader.newModule({
        prepareGlobal: function(moduleName) {
          // store a complete copy of the global object
          // in order to detect changes
          curGlobalObj = {};

          for (var g in __global) {
            if (indexOf.call(ignoredGlobalProps, g) != -1)
              continue;
            if (!hasOwnProperty || __global.hasOwnProperty(g)) {
              try {
                curGlobalObj[g] = __global[g];
              }
              catch (e) {
                ignoredGlobalProps.push(g);
              }
            }
          }
        },
        retrieveGlobal: function(moduleName) {
          var singleGlobal;
          var multipleExports;
          var exports;

          for (var g in __global) {
            if (indexOf.call(ignoredGlobalProps, g) != -1)
              continue;

            var value = __global[g];

            if ((!hasOwnProperty || __global.hasOwnProperty(g)) && g !== __global && curGlobalObj[g] !== value) {
              if (!exports) {
                // first property found
                exports = {};
                singleGlobal = value;
              }
              
              exports[g] = value;
              
              if (!multipleExports && singleGlobal !== value)
                multipleExports = true;
            }
          }

          return multipleExports ? exports : singleGlobal;
        }
      }));
    };
  });

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

  // ideally we could support script loading for globals, but the issue with that is that
  // we can't do it with AMD support side-by-side since AMD support means defining the
  // global define, and global support means not definining it, yet we don't have any hook
  // into the "pre-execution" phase of a script tag being loaded to handle both cases

  hook('instantiate', function(instantiate) {
    return function(load) {
      var loader = this;

      if (!load.metadata.format)
        load.metadata.format = 'global';

      // global is a fallback module format
      if (load.metadata.format == 'global') {
        load.metadata.execute = function(require, exports, module) {

          var exportName = load.metadata.exports;

          if (!exportName)
            loader.get('@@global-helpers').prepareGlobal(module.id);
          else
            load.source += '\nthis["' + exportName + '"] = ' + exportName + ';';

          // disable module detection
          var define = __global.define;
          var require = __global.require;
          
          __global.define = undefined;
          __global.module = undefined;
          __global.exports = undefined;

          // allow globals to be defined by other modules (including non globals)
          if (load.metadata.globals) {
            var globals = {};
            for (var g in load.metadata.globals)
              globals[g] = require(load.metadata.globals[g]);
          }

          __exec(load, globals);

          __global.require = require;
          __global.define = define;

          if (exportName)
            return readGlobalProperty(exportName, __global);
          else
            return loader.get('@@global-helpers').retrieveGlobal(module.id);
        }
      }
      return instantiate.call(this, load);
    };
  });
})();