mini javascript loader

自己写的一个mini 且 simple 的 javascript loader

功能特点

• 异步并行载入js, 每个js只加载一次
• 支持模块依赖, 未检测循环依赖
• 支持别名
• 兼容ie6+ , firefox, chrome ...
• API : 
    define.alias['modName'] = 'http://path/to/mods/root/dir'
    define(deps, callback)   其中 callback(dep1, dep2, dep3...)
    require(deps, callback)   其中 callback(dep1, dep2, dep3...)

define = (function() {
	
	var modules = {};
	var modulesCallbacks = {};
	var alias = window.alias || {};

	function map(arr, callback) {
		var ret = [];
		for(var i = 0; i < arr.length; i++) {
			ret.push(callback(arr[i], i, arr));
		}
		return ret;
	}
	function isString(obj) {
		return typeof(obj) == 'string';
	}
	function isArray(obj) {
		return Object.prototype.toString.call(obj) == '[object Array]';
	}
	function isFunction(obj) {
		return typeof(obj) == 'function';
	}
	function mix(src, dst) {
		for(var key in dst) {
			src[key] = dst[key];
		}
	}
	function getScript(url, callback) {
		var node = document.createElement("script");
		node.async = true;
		if (document.addEventListener) {
			node.addEventListener('load', callback);
		} else {
			node.onreadystatechange = function () {
				if(node.readyState == 'loaded' || node.readyState == 'complete') {
					callback && callback();
				}
			}
		}
		node.src = url;

		var head = document.head || document.getElementsByTagName('head')[0] || document.documentElement;
		head.insertBefore(node, head.firstChild);
		return node;
	}

	function getCurrentScript() {
		
		//firefox4 and opera
		if (document.currentScript) {
			return document.currentScript;
		} else if (document.attachEvent) {
			//ie6-9 得到当前正在执行的script标签
			var scripts = document.getElementsByTagName('script');
			for (var i = scripts.length - 1; i > -1; i--) {
				if (scripts[i].readyState === 'interactive') {
					return scripts[i];
				}
			}
		} else {
			// 参考 https://github.com/samyk/jiagra/blob/master/jiagra.js
			// chrome and firefox4以前的版本
			var stack;
			try {
				makeReferenceError
			} catch (e) {
				stack = e.stack;
			}
			if (!stack)
				return undefined;
			// chrome uses at, ff uses @

			var e = stack.indexOf(' at ') !== -1 ? ' at ' : '@';
			while (stack.indexOf(e) !== -1) {
				stack = stack.substring(stack.indexOf(e) + e.length);
			}
			stack = stack.replace(/:\d+:\d+$/ig, "");

			var scripts = document.getElementsByTagName('script');
			for (var i = scripts.length - 1; i > -1; i--) {
				if (scripts[i].src === stack) {
					return scripts[i];
				}
			}
		}
	}

	function getScriptWithCache(url, callback) {
		var scripts = this._scripts = this._scripts || {};
		var cache = scripts[url];
		if (cache === true) {
			callback && callback();
			return ;
		} else if (isArray(cache)) {
			cache.push(callback);
			return ;
		} else {
			scripts[url] = [callback];
		}

		getScript(url, function() {
			var callbacks = scripts[url] || [];
			scripts[url] = true;
			for(var i = 0; i < callbacks.length; i++) {
				callbacks[i] && callbacks[i]();
			}
		});		
	}

	function getModule(mod, callback) {
		if (!modules[mod]) {
			modulesCallbacks[mod] = modulesCallbacks[mod] || [];
			modulesCallbacks[mod].push(callback);

			getScriptWithCache(mod);
		} else {
			callback && callback(modules[mod]);
		}
	}

	function getModules(mods, callback) {
		if (mods == undefined || mods.length == 0) {
			callback && callback();
			return ;
		}
		var c = 0;

		var ret = [];
		map(mods, function(mod, i) {
			getModule(mod, function(obj) {
				ret[i] = obj;

				if (++c == mods.length) {
					callback && callback(ret);
				}
			});
		});
	}

	function define(deps, callback) {
		var container = this;

		if (!isString(deps) && !isArray(deps)) {
			callback = deps;
			deps = [];
		}
		var current = getCurrentScript();
		var url = current && current.src;

		deps = deps || [];
		if (isString(deps)) {
			deps = deps.split(',');
		}
		var allDeps = map(deps, tran);				//全部转换映射

		getModules(allDeps, function(mods) {
			var ret = isFunction(callback) ? callback.apply(undefined, mods||[]) : callback;
			modules[url] = modules[url] || {}
			mix(modules[url], ret);

			container != window && (mix(container, ret));

			if (modulesCallbacks[url]) {
				for(var i = 0; i < modulesCallbacks[url].length; i++) {
					modulesCallbacks[url][i](ret);
				}
			}
		});

		return container;
	}

	function tran(dep) {
		for(var key in alias) {
			dep = dep.replace(new RegExp('^' + key), alias[key]);		//TODO
		}
		return dep + '.js';
	}

	define.alias = alias;
	return define;
})();

测试用例

//上述代码保存为 http://localhost/loader/loader.js

<!-- index.htm -->
<script src="loader.js"></script>

<script>
define.alias['ok'] = 'http://localhost/loader/';
define(['ok/mod1', 'ok/mod2'], function(Mod1, Mod2) {
	console.log('execute index ', Mod1, Mod2);
});
</script>

//   http://localhost/loader/mod1.js
require(['ok/mod2'], function(Mod2) {
	console.log('mod1 index ', Mod2);

	return {
		mod1: 'this is mod1'
	}
});

//   http://localhost/loader/mod2.js
define(function() {
	console.log('mod2 index ');

	return {
		'hello' : 'world'
	}
});

补: 其它用法

//mod3.js
//功能模块1
define({
    sayHello : function() {
       console.log('hello');
    }
});

//功能模块2, 模块2没支持!!!
define(function() {
    return {
        sayWorld : function() {
           console.log('world');
        }
    }
});

App = {define : define, require: define};
App.define.alias['ok'] = 'http://lhj/loader';
App.define({
      showMsg : function(msg) {
          console.log(msg);
      }
});

App.define(function(Mod3) {
      return {
          say : function() {
				App.require('ok/Mod3', function(Mod3) {
	                  return Mod3.sayHello() + ' ' + '';//Mod3.sayWorld();
				});
          }
      }
});

App.showMsg(123);
App.say();