requirejs源码分析: requirejs 方法–2. context.require(deps, callback, errback);

上一篇 requirejs源码分析: requirejs 方法–1. 主入口  中的return context.require(deps, callback, errback);  调用的是makeRequire方法中的localRequire

function localRequire(deps, callback, errback) {
    var id, map, requireMod;

    if (options.enableBuildCallback && callback && isFunction(callback)) {
        callback.__requireJsBuild = true;
    }

    if (typeof deps === 'string') {
        if (isFunction(callback)) {
            //Invalid call
            return onError(makeError('requireargs', 'Invalid require call'), errback);
        }

        //If require|exports|module are requested, get the
        //value for them from the special handlers. Caveat:
        //this only works while module is being defined.
        if (relMap && hasProp(handlers, deps)) {
            return handlers[deps](registry[relMap.id]);
        }

        //Synchronous access to one module. If require.get is
        //available (as in the Node adapter), prefer that.
        if (req.get) {
            return req.get(context, deps, relMap, localRequire);
        }

        //Normalize module name, if it contains . or ..
        map = makeModuleMap(deps, relMap, false, true);
        id = map.id;

        if (!hasProp(defined, id)) {
            return onError(makeError('notloaded', 'Module name "' +
                        id +
                        '" has not been loaded yet for context: ' +
                        contextName +
                        (relMap ? '' : '. Use require([])')));
        }
        return defined[id];
    }

    //Grab defines waiting in the global queue.
    intakeDefines();

   //Mark all the dependencies as needing to be loaded.
    context.nextTick(function () {
        //Some defines could have been added since the
        //require call, collect them.
        intakeDefines();

        //实例化Module对象                   
        requireMod = getModule(makeModuleMap(null, relMap));

        //Store if map config should be applied to this require
        //call for dependencies.
        requireMod.skipMap = options.skipMap;

        //初始化 Module 对象
        requireMod.init(deps, callback, errback, {
            enabled: true
        });

        checkLoaded();
    });

    return localRequire;
}

这里主要是方法：

context.nextTick(function () {
        //Some defines could have been added since the
        //require call, collect them.
        intakeDefines();

        //实例化Module对象                   
        requireMod = getModule(makeModuleMap(null, relMap));

        //Store if map config should be applied to this require
        //call for dependencies.
        requireMod.skipMap = options.skipMap;

        //初始化 Module 对象
        requireMod.init(deps, callback, errback, {
            enabled: true
        });

        checkLoaded();
    });

这里使用context.nextTick是延迟4ms再执行（异步）。 这里不能很理解作者的目的。 是为了不卡主线程？

该方法主要流程：
1. 实例化Module。

requireMod = getModule(makeModuleMap(null, relMap));

        Module也是上下文newContext里的对象。这个是核心模块。包含以下主要的属性。

this.events = getOwn(undefEvents, map.id) || {};
this.map = map;
this.shim = getOwn(config.shim, map.id);
this.depExports = [];
this.depMaps = [];
this.depMatched = [];
this.pluginMaps = {};
this.depCount = 0;

该对象是封装模块，存在模块信息（shim,依赖等。）。 还包含对模块的加载，依赖加载，通知依赖等。