require.js源码分析
浏览数：58 /
时间：2015年06月09日
写的寥寥草草，博客园的布局怎么弄还没有研究，再保存一份草稿，日后在完善，深度研究
require.js 加载顺序
1：加载html主页，require.js文件
2：脚本执行到html中的script开始使用require.js进行模块化加载。先将文件路径加载保存在map中。在调用require()时并没有进行相应文件的加载
3：require配置，在初始化config中到底做了些什么事情呢（真正对用的初始化函数是function(deps, callback, errback, optional)这里包括了需要定义的config基本属性，回掉函数，错误处理函数，optional）
3.1确定context使用require.js中默认的定义
3.2config基本属性不是数组与字符串（在这里的数组判断挺有意思，没有使用typeof而是使用了Object.prototype.toString.call native方法）：{
保存的config基本属性
如果第二个参数数组，则callback默认也是config基本属性的一项
}
3.3config基本属性中是否包含context项
3.4验证是否已经拥有该context，同样使用了Objet.prototype.hasOwnProperty.call native方法。contextName毕竟只是一个临时变量，真正最后要用的还是require.js中的刚开始声明的那些全局变量
3.5最后将config基本属性添加到context上下文本对象中的config属性中，默认的一个config包含了如上几个基本属性
eachProp(cfg, function (value, prop) {
if (objs[prop]) {
if (!config[prop]) {
config[prop] = {};
}
mixin(config[prop], value, true, true);
} else {
config[prop] = value;
}
});
function eachProp(obj, func) {
var prop;
for (prop in obj) {
if (hasProp(obj, prop)) {
if (func(obj[prop], prop)) {
break;
}
}
}
}
function mixin(target, source, force, deepStringMixin) {
if (source) {
eachProp(source, function (value, prop) {
if (force || !hasProp(target, prop)) {
if (deepStringMixin && typeof value === ‘object‘ && value &&
!isArray(value) && !isFunction(value) &&
!(value instanceof RegExp)) {
if (!target[prop]) {
target[prop] = {};
}
mixin(target[prop], value, force, deepStringMixin);
} else {
target[prop] = value;
}
}
});
}
return target;
}
function each(ary, func) {
if (ary) {
var i;
for (i = 0; i < ary.length; i += 1) {
if (ary[i] && func(ary[i], i, ary)) {
break;
}
}
}
}
但是在eachProp中我们也看到了，可以添加自定义属性，mixin config中 ，packages必须是数组，其他都是object对象，
3.6创建上下文对象context的equire属性。至此所有的script中的顺序动作已经完成了
makeRequire: function (relMap, options) {
options = options || {};
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();
requireMod = getModule(makeModuleMap(null, relMap));
//Store if map config should be applied to this require
//call for dependencies.
requireMod.skipMap = options.skipMap;
requireMod.init(deps, callback, errback, {
enabled: true
});
checkLoaded();
});
return localRequire;
}
mixin(localRequire, {
isBrowser: isBrowser,
/**
* Converts a module name + .extension into an URL path.
* *Requires* the use of a module name. It does not support using
* plain URLs like nameToUrl.
*/
toUrl: function (moduleNamePlusExt) {
var ext,
index = moduleNamePlusExt.lastIndexOf(‘.‘),
segment = moduleNamePlusExt.split(‘/‘)[0],
isRelative = segment === ‘.‘ || segment === ‘..‘;
//Have a file extension alias, and it is not the
//dots from a relative path.
if (index !== -1 && (!isRelative || index > 1)) {
ext = moduleNamePlusExt.substring(index, moduleNamePlusExt.length);
moduleNamePlusExt = moduleNamePlusExt.substring(0, index);
}
return context.nameToUrl(normalize(moduleNamePlusExt,
relMap && relMap.id, true), ext, true);
},
defined: function (id) {
return hasProp(defined, makeModuleMap(id, relMap, false, true).id);
},
specified: function (id) {
id = makeModuleMap(id, relMap, false, true).id;
return hasProp(defined, id) || hasProp(registry, id);
}
});
//Only allow undef on top level require calls
if (!relMap) {
localRequire.undef = function (id) {
//Bind any waiting define() calls to this context,
//fix for #408
takeGlobalQueue();
var map = makeModuleMap(id, relMap, true),
mod = getOwn(registry, id);
removeScript(id);
delete defined[id];
delete urlFetched[map.url];
delete undefEvents[id];
//Clean queued defines too. Go backwards
//in array so that the splices do not
//mess up the iteration.
eachReverse(defQueue, function(args, i) {
if(args[0] === id) {
defQueue.splice(i, 1);
}
});
if (mod) {
//Hold on to listeners in case the
//module will be attempted to be reloaded
//using a different config.
if (mod.events.defined) {
undefEvents[id] = mod.events;
}
cleanRegistry(id);
}
};
}
return localRequire;
},
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);
}
}
}
但是在require属性中有启用一个setTimeout定时间隔任务
req.nextTick = typeof setTimeout !== ‘undefined‘ ? function (fn) {
setTimeout(fn, 4);
} : function (fn) { fn(); };
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);
}
}
}
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, 0].concat(globalDefQueue));
globalDefQueue = [];
}
}
获取module
function getModule(depMap) {
var id = depMap.id,
mod = getOwn(registry, id);
if (!mod) {
mod = registry[id] = new context.Module(depMap);
}
return mod;
}
经过几次循环调用后，终于load到了第一个moudle，是在makeModuleMap方法中url等信息的拼装，保存到了depMaps中。同时depCount的计数值也加一了。这也就是require.js最重要的模块化，将所有的要加载文件通过一个map对下保存，每个文件用require.js的moudle进行封装，封装了什么东西呢？
这个封装而不是单独的封装一个module对象，而是先进性了require的对象-》context对象-》module对象
对于module的加载过程中函数的执行顺序？
nextTick循环调用
-intakeDefines
--takeGlobalQueue
-getModule
--makeModuleMap
---splitPrefix
---normalize
----trimDots
---splitPrefix
---nameToUrl
---Module
-Module.init
--Module.enable
---Module.enable
---Module.check
---Module.emit
-checkLoaded
注意：如果通过require.js模块加载的第一个文件加载进来后，因为require.js还没有结束，DOM加载还需要继续，所以还会顺序运行新进来的文件。
check
fetch
enable
callPlugin
load
跳回到context
load
跳回到require
load
最后真正实用的还是req.load加载js，那到底是怎么加载的呢？
req.load = function (context, moduleName, url) {
var config = (context && context.config) || {},
node;
if (isBrowser) {
//In the browser so use a script tag
node = req.createNode(config, moduleName, url);
node.setAttribute(‘data-requirecontext‘, context.contextName);
node.setAttribute(‘data-requiremodule‘, moduleName);
//Set up load listener. Test attachEvent first because IE9 has
//a subtle issue in its addEventListener and script onload firings
//that do not match the behavior of all other browsers with
//addEventListener support, which fire the onload event for a
//script right after the script execution. See:
//https://connect.microsoft.com/IE/feedback/details/648057/script-onload-event-is-not-fired-immediately-after-script-execution
//UNFORTUNATELY Opera implements attachEvent but does not follow the script
//script execution mode.
if (node.attachEvent &&
//Check if node.attachEvent is artificially added by custom script or
//natively supported by browser
//read https://github.com/jrburke/requirejs/issues/187
//if we can NOT find [native code] then it must NOT natively supported.
//in IE8, node.attachEvent does not have toString()
//Note the test for "[native code" with no closing brace, see:
//https://github.com/jrburke/requirejs/issues/273
!(node.attachEvent.toString && node.attachEvent.toString().indexOf(‘[native code‘) < 0) &&
!isOpera) {
//Probably IE. IE (at least 6-8) do not fire
//script onload right after executing the script, so
//we cannot tie the anonymous define call to a name.
//However, IE reports the script as being in ‘interactive‘
//readyState at the time of the define call.
useInteractive = true;
node.attachEvent(‘onreadystatechange‘, context.onScriptLoad);
//It would be great to add an error handler here to catch
//404s in IE9+. However, onreadystatechange will fire before
//the error handler, so that does not help. If addEventListener
//is used, then IE will fire error before load, but we cannot
//use that pathway given the connect.microsoft.com issue
//mentioned above about not doing the ‘script execute,
//then fire the script load event listener before execute
//next script‘ that other browsers do.
//Best hope: IE10 fixes the issues,
//and then destroys all installs of IE 6-9.
//node.attachEvent(‘onerror‘, context.onScriptError);
} else {
node.addEventListener(‘load‘, context.onScriptLoad, false);
node.addEventListener(‘error‘, context.onScriptError, false);
}
node.src = url;
//For some cache cases in IE 6-8, the script executes before the end
//of the appendChild execution, so to tie an anonymous define
//call to the module name (which is stored on the node), hold on
//to a reference to this node, but clear after the DOM insertion.
currentlyAddingScript = node;
if (baseElement) {
head.insertBefore(node, baseElement);
} else {
head.appendChild(node);
}
currentlyAddingScript = null;
return node;
} else if (isWebWorker) {
try {
//In a web worker, use importScripts. This is not a very
//efficient use of importScripts, importScripts will block until
//its script is downloaded and evaluated. However, if web workers
//are in play, the expectation that a build has been done so that
//only one script needs to be loaded anyway. This may need to be
//reevaluated if other use cases become common.
importScripts(url);
//Account for anonymous modules
context.completeLoad(moduleName);
} catch (e) {
context.onError(makeError(‘importscripts‘,
‘importScripts failed for ‘ +
moduleName + ‘ at ‘ + url,
e,
[moduleName]));
}
}
};
创建一个Node
req.createNode = function (config, moduleName, url) {
var node = config.xhtml ?
document.createElementNS(‘http://www.w3.org/1999/xhtml‘, ‘html:script‘) :
document.createElement(‘script‘);
node.type = config.scriptType || ‘text/javascript‘;
node.charset = ‘utf-8‘;
node.async = true;
return node;
};
继续组装script node head = s.head = document.getElementsByTagName(‘head‘)[0];
在这里require.Js将script node添加到了原始html中的head标签内
新生成的head，同时浏览器也对js文件进行了加载
最后有意思的是require.js在checkLoaded时竟然做了一遍remove，这个还是蛮有意思的，
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