jq的选择器流程分析开篇

本文简单地分析以下jquery的选择器流程：

 

为了考量jq的版本优化，这篇的代码分析来自jq1.3

 

 

/*
 * @param selector 
 * @param context
 * @info $的入口
*/
var jQuery = window.jQuery = window.$ = function(selector,context){
       return new jQuery.fn.init(selector,context);
}

 

 

var quickExpr = /^[^<]*(<(.|\s)+>)[^>]*$|^#([\w-]+)$/;

jQuery.fn = jQuery.prototype = {
       /*
        * @name init
        * @param selector
        * @param context
       */
       init:function(selector,context){
             //默认是document
             selector = selector || document;
             
             //selector为DOM Element
             if(selector.nodeType){
                   this[0] = selector;
                   this.length = 1;
                   this.context = selector;
                   return this;
             }


             //selector为string
             if(typeof selector === "string"){
                   //比如#test 返回的match为["#test",undefined,undefined,"test"];
                  //比如<div id="test">test</div>返回的match为：['<div id="test">test</div>','<div id="test">test</div>','v',undefined];
                   var match = quickExpr.exec(selector);

                   if(match && (match[1] || !context)){

                         if(match[1]){
                              selector = jQuery.clean([match[1]],context);

                         }else{

                              //$("#ID")
                              var elem = document.getElementById(match[3]);
                              if(elem){
                                     if(elem.id != match [3]){
                                           return jQuery().find(selector);
                                     }

                                     var ret = jQuery(elem);
                                     ret.context = document;
                                     ret.selector = selector;
                                     return ret;

                              }
                              selector = [];
                         
                         }


                   }else{

                          //$(expr,[context])  ===>  $(content).find(expr)
                          return jQuery(context).find(selector); 
                   }                   

             }else if(jQuery.isFunction(selector)){

                   //很多简写的方式：$(function(){});
                    return jQuery(document).ready(selector); 
             }


             if(seletor.selector && selector.context){
                    this.selector = selector.selector;
                    this.context = selector.context;
             }

              return this.setArray(jQuery.makeArray(selector));
    
       }

}