jQuery源码分析（一）

生成jQuery对象

var global = typeof window !== "undefined" ? window : this;
var factory //line 40 第二个参数
( function( global, factory ) {

	"use strict";

	if ( typeof module === "object" && typeof module.exports === "object" ) {

		// For CommonJS and CommonJS-like environments where a proper `window`
		// is present, execute the factory and get jQuery.
		// For environments that do not have a `window` with a `document`
		// (such as Node.js), expose a factory as module.exports.
		// This accentuates the need for the creation of a real `window`.
		// e.g. var jQuery = require("jquery")(window);
		// See ticket #14549 for more info.
		module.exports = global.document ?
			factory( global, true ) :
			function( w ) {
				if ( !w.document ) {
					throw new Error( "jQuery requires a window with a document" );
				}
				return factory( w );
			};
	} else {
		factory( global );
	}

// Pass this if window is not defined yet
} )(global, factory);

如果当前容器没用window对象，那么将this作为最父层。factory()函数将会返回jQuery对象。

在CommonJS 或者 CommonJS-like 的环境下 window 对象是没有问题的；如果一个执行环境，它的“window”对象没有“document”的属性，例如Node.js。那么需要暴露一个factory()方法，并将真实的“window”对象传入。var jQuery = require(“jquery”)(window);

通过下面这个代码片段我们可以验证，在nodejs中没有 window对象

router.get('/jquery/window', function(req, res, next) {
    console.log("window:" + typeof window);
    //window:undefined
    res.end();
});

定义公共属性和工具方法

line:48 - line:144

var arr = [];

var document = window.document;

var getProto = Object.getPrototypeOf;

var slice = arr.slice;

var concat = arr.concat;

var push = arr.push;

var indexOf = arr.indexOf;

var class2type = {};

var toString = class2type.toString;

var hasOwn = class2type.hasOwnProperty;

var fnToString = hasOwn.toString;

var ObjectFunctionString = fnToString.call(Object);

var support = {};

通过这种方式避免后面调用过程中一行代码过长

isFunction 判断是否是函数

var isFunction = function isFunction( obj ) {
	// Support: Chrome <=57, Firefox <=52
	// In some browsers, typeof returns "function" for HTML