/**
* Internal method to transfer globalQueue items to this context‘s
* defQueue.
*/
function takeGlobalQueue() {
  //Push all the globalDefQueue items into the context‘s defQueue
  if (globalDefQueue.length) {
    //Array splice in the values since the context code has a
    //local var ref to defQueue, so cannot just reassign the one
    //on context.
    apsp.apply(defQueue, [defQueue.length - 1, 0].concat(globalDefQueue));
    globalDefQueue = [];
  }
}

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function intakeDefines() {
  var args;
  //Any defined modules in the global queue, intake them now.
  takeGlobalQueue();
  //Make sure any remaining defQueue items get properly processed.
  while (defQueue.length) {
    args = defQueue.shift();
    if (args[0] === null) {
      return onError(makeError(‘mismatch‘, ‘Mismatched anonymous define() module: ‘ + args[args.length - 1]));
    } else {
      //args are id, deps, factory. Should be normalized by the
      //define() function.
      callGetModule(args);
    }
  }
}

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function callGetModule(args) {
  //Skip modules already defined.
  if (!hasProp(defined, args[0])) {
    getModule(makeModuleMap(args[0], null, true)).init(args[1], args[2]);
  }
}

/**
* callback for script loads, used to check status of loading.
*
* @param {Event} evt the event from the browser for the script
* that was loaded.
*/
onScriptLoad: function (evt) {
  //Using currentTarget instead of target for Firefox 2.0‘s sake. Not
  //all old browsers will be supported, but this one was easy enough
  //to support and still makes sense.
  if (evt.type === ‘load‘ ||
            (readyRegExp.test((evt.currentTarget || evt.srcElement).readyState))) {
    //Reset interactive script so a script node is not held onto for
    //to long.
    interactiveScript = null;

    //Pull out the name of the module and the context.
    var data = getScriptData(evt);
    context.completeLoad(data.id);
  }
},

req.nextTick = typeof setTimeout !== ‘undefined‘ ? function (fn) {
  setTimeout(fn, 4);
} : function (fn) { fn(); };

req.nextTick = function (fn){ fn();};

if (this.map.isDefine && !this.ignore) {
  defined[id] = exports;

  if (req.onResourceLoad) {
    req.onResourceLoad(context, this.map, this.depMaps);
  }
}

if (this.defined && !this.defineEmitted) {
  this.defineEmitted = true;
  this.emit(‘defined‘, this.exports);
  this.defineEmitComplete = true;
}

contexts._.defined
Object {}

require([‘name‘, ‘say‘], function (name, say) {
  say(name);
});

require([‘name‘, ‘say‘], function (name, say) {
  say(name);
});

 return context.require(deps, callback, errback);

contexts._.defined => Object {main: undefined}

this.factory = factory;

this.depMaps = depMaps && depMaps.slice(0);

//Enable each dependency
each(this.depMaps, bind(this, function (depMap, i) {
  var id, mod, handler;

  if (typeof depMap === ‘string‘) {
    //Dependency needs to be converted to a depMap
    //and wired up to this module.
    depMap = makeModuleMap(depMap,
                                  (this.map.isDefine ? this.map : this.map.parentMap),
                                  false,
                                  !this.skipMap);
    this.depMaps[i] = depMap;

    handler = getOwn(handlers, depMap.id);

    if (handler) {
      this.depExports[i] = handler(this);
      return;
    }

    this.depCount += 1;

    on(depMap, ‘defined‘, bind(this, function (depExports) {
      this.defineDep(i, depExports);
      this.check();
    }));

    if (this.errback) {
      on(depMap, ‘error‘, bind(this, this.errback));
    }
  }

  id = depMap.id;
  mod = registry[id];

  //Skip special modules like ‘require‘, ‘exports‘, ‘module‘
  //Also, don‘t call enable if it is already enabled,
  //important in circular dependency cases.
  if (!hasProp(handlers, id) && mod && !mod.enabled) {
    context.enable(depMap, this);
  }
}));

requireMod.init(deps, callback, errback, {
  enabled: true
});

function checkLoaded() {
  var map, modId, err, usingPathFallback,
            waitInterval = config.waitSeconds * 1000,
  //It is possible to disable the wait interval by using waitSeconds of 0.
            expired = waitInterval && (context.startTime + waitInterval) < new Date().getTime(),
            noLoads = [],
            reqCalls = [],
            stillLoading = false,
            needCycleCheck = true;

  //Do not bother if this call was a result of a cycle break.
  if (inCheckLoaded) {
    return;
  }

  inCheckLoaded = true;

  //Figure out the state of all the modules.
  eachProp(enabledRegistry, function (mod) {
    map = mod.map;
    modId = map.id;

    //Skip things that are not enabled or in error state.
    if (!mod.enabled) {
      return;
    }

    if (!map.isDefine) {
      reqCalls.push(mod);
    }

    if (!mod.error) {
      //If the module should be executed, and it has not
      //been inited and time is up, remember it.
      if (!mod.inited && expired) {
        if (hasPathFallback(modId)) {
          usingPathFallback = true;
          stillLoading = true;
        } else {
          noLoads.push(modId);
          removeScript(modId);
        }
      } else if (!mod.inited && mod.fetched && map.isDefine) {
        stillLoading = true;
        if (!map.prefix) {
          //No reason to keep looking for unfinished
          //loading. If the only stillLoading is a
          //plugin resource though, keep going,
          //because it may be that a plugin resource
          //is waiting on a non-plugin cycle.
          return (needCycleCheck = false);
        }
      }
    }
  });

  if (expired && noLoads.length) {
    //If wait time expired, throw error of unloaded modules.
    err = makeError(‘timeout‘, ‘Load timeout for modules: ‘ + noLoads, null, noLoads);
    err.contextName = context.contextName;
    return onError(err);
  }

  //Not expired, check for a cycle.
  if (needCycleCheck) {
    each(reqCalls, function (mod) {
      breakCycle(mod, {}, {});
    });
  }

  //If still waiting on loads, and the waiting load is something
  //other than a plugin resource, or there are still outstanding
  //scripts, then just try back later.
  if ((!expired || usingPathFallback) && stillLoading) {
    //Something is still waiting to load. Wait for it, but only
    //if a timeout is not already in effect.
    if ((isBrowser || isWebWorker) && !checkLoadedTimeoutId) {
      checkLoadedTimeoutId = setTimeout(function () {
        checkLoadedTimeoutId = 0;
        checkLoaded();
      }, 50);
    }
  }

  inCheckLoaded = false;
}

if ((!expired || usingPathFallback) && stillLoading) {
  //Something is still waiting to load. Wait for it, but only
  //if a timeout is not already in effect.
  if ((isBrowser || isWebWorker) && !checkLoadedTimeoutId) {
    checkLoadedTimeoutId = setTimeout(function () {
      checkLoadedTimeoutId = 0;
      checkLoaded();
    }, 50);
  }
}

 this.inited = true;

//nextTick
requireMod.init(deps, callback, errback, {
  enabled: true
});

if (options.enabled || this.enabled) {
  //Enable this module and dependencies.
  //Will call this.check()
  this.enable();
} else {
  this.check();
}

each(this.depMaps, bind(this, function (depMap, i) {
  var id, mod, handler;

  if (typeof depMap === ‘string‘) {
    //Dependency needs to be converted to a depMap
    //and wired up to this module.
    depMap = makeModuleMap(depMap,
                                  (this.map.isDefine ? this.map : this.map.parentMap),
                                  false,
                                  !this.skipMap);
    this.depMaps[i] = depMap;

    handler = getOwn(handlers, depMap.id);

    if (handler) {
      this.depExports[i] = handler(this);
      return;
    }

    this.depCount += 1;

    on(depMap, ‘defined‘, bind(this, function (depExports) {
      this.defineDep(i, depExports);
      this.check();
    }));

    if (this.errback) {
      on(depMap, ‘error‘, bind(this, this.errback));
    }
  }

  id = depMap.id;
  mod = registry[id];

  //Skip special modules like ‘require‘, ‘exports‘, ‘module‘
  //Also, don‘t call enable if it is already enabled,
  //important in circular dependency cases.
  if (!hasProp(handlers, id) && mod && !mod.enabled) {
    context.enable(depMap, this);
  }
}));

this.defined = true;

//注册点
on(depMap, ‘defined‘, bind(this, function (depExports) {
  this.defineDep(i, depExports);
  this.check();
}));

//触发点
this.emit(‘defined‘, this.exports);

//关键点，用于消除依赖
this.defineDep(i, depExports);