JQuery日记 5.31 JQuery对象的生成

JQuery对象的生成

1 selector为任何可转换false的空值

  返回空JQuery对象

2 selector为字符串

  2.1 selector为html字符串或有id属性的标签

      2.2.1 selector为html字符时

            转换html字符为DOM元素并放入当前JQuery的数组

            当context参数为js对象时,迭代器属性

            (1)当前属性对应此JQuery对象的某个函数时,调用此JQuery对象的此函数,参数为当前属性的值.

            (2)其他设置HTML属性

      2.2.2 selector有id时

            直接getElementById

  2.2 selector为选择器表达式

      修正context在context上调用find方法

3 selector为DOM元素

  包装此DOM为JQuery对象

4 selector为函数

  此函数作为ready时间监听器

5 selector为函数及不满足前四个分支的情况

  将此selecotr放入当前JQuery对象数组中

init = jQuery.fn.init = function( selector, context ) {var match, elem;// HANDLE: $(""), $(null), $(undefined), $(false)// 返回空JQuery对象if ( !selector ) {return this;}// Handle HTML stringsif ( typeof selector === "string" ) {// 如果selector以'<'开头以'>'结尾并且长度大于3认为其是HTML字符串,不进行rquickExpr匹配if ( selector[0] === "<" && selector[ selector.length - 1 ] === ">" && selector.length >= 3 ) {// Assume that strings that start and end with <> are HTML and skip the regex checkmatch = [ null, selector, null ];} else {match = rquickExpr.exec( selector );}// Match html or make sure no context is specified for #idif ( match && (match[1] || !context) ) {// HANDLE: $(html) -> $(array)if ( match[1] ) {// 如果context是jquery对象,取第一个DOM元素context = context instanceof jQuery ? context[0] : context;// scripts is true for back-compat// Intentionally let the error be thrown if parseHTML is not present// 将HTML转换后的DOM元素合并当到当前jquery对象jQuery.merge( this, jQuery.parseHTML(match[1],context && context.nodeType ? context.ownerDocument || context : document,true) );// HANDLE: $(html, props)// 处理第一个参数为HTML字符串第二个参数为JS对象if ( rsingleTag.test( match[1] ) && jQuery.isPlainObject( context ) ) {// for-each context中元素for ( match in context ) {// Properties of context are called as methods if possible// 如果当前JQuery对象match属性是函数if ( jQuery.isFunction( this[ match ] ) ) {// 执行match函数 this[ match ]( context[ match ] );// ...and otherwise set as attributes// 否则,设置HTML属性} else {this.attr( match, context[ match ] );}}}return this;// HANDLE: $(#id)} else {elem = document.getElementById( match[2] );// Check parentNode to catch when Blackberry 4.6 returns// nodes that are no longer in the document #6963// Blackberry 4.6缓存过度，不在document中的node仍然查找的到if ( elem && elem.parentNode ) {// Inject the element directly into the jQuery objectthis.length = 1;this[0] = elem;}// 设置上下文对象为documentthis.context = document;this.selector = selector;return this;}// HANDLE: $(expr, $(...))// 处理没有context参数或context参数是JQuery对象} else if ( !context || context.jquery ) {// 如果没有context参数则在document范围内调用find方法查找// 如果有context参数则在本context范围内查找return ( context || rootjQuery ).find( selector );// HANDLE: $(expr, context)// (which is just equivalent to: $(context).find(expr)// 处理selector为expr,第二个参数也为context的selector的情况} else {// 对context进行选择再findreturn this.constructor( context ).find( selector );}// HANDLE: $(DOMElement)// 将DOM元素包裹为JQuery对象} else if ( selector.nodeType ) {this.context = this[0] = selector;this.length = 1;return this;// HANDLE: $(function)// Shortcut for document ready// 如果selector是function// 将function绑定为ready监听,或立即执行(rootjQuery.ready === "undefined")} else if ( jQuery.isFunction( selector ) ) {return typeof rootjQuery.ready !== "undefined" ?rootjQuery.ready( selector ) :// Execute immediately if ready is not presentselector( jQuery );}// 如果selctor是函数或对象时，且有selector元素时if ( selector.selector !== undefined ) {this.selector = selector.selector;this.context = selector.context;}// 将selector放入当前JQuery对象的数组里return jQuery.makeArray( selector, this );};