jQuery源码中的Ajax--load方法

　　load()方法是jQuery中最为简单和常用的方法，能载入远程HTML代码幷插入到DOM中，其结构为：

load(url [.data] [.callback])

　　各参数解释如下：

　　load的源码如下：（源码目录：jquery/src/ajax/load.js）

define( [
    "../core",
    "../core/parseHTML",
    "../ajax",
    "../traversing",
    "../manipulation",
    "../selector"
], function( jQuery ) {

"use strict";

/**
 * Load a url into a page
 */
jQuery.fn.load = function( url, params, callback ) {
    var selector, type, response,
        self = this,
        off = url.indexOf( " " );

    if ( off > -1 ) {
        selector = jQuery.trim( url.slice( off ) );
        url = url.slice( 0, off );
    }

    // If it‘s a function
    if ( jQuery.isFunction( params ) ) {

        // We assume that it‘s the callback
        callback = params;
        params = undefined;

    // Otherwise, build a param string
    } else if ( params && typeof params === "object" ) {
        type = "POST";
    }

    // If we have elements to modify, make the request
    if ( self.length > 0 ) {
        jQuery.ajax( {
            url: url,

            // If "type" variable is undefined, then "GET" method will be used.
            // Make value of this field explicit since
            // user can override it through ajaxSetup method
            type: type || "GET",
            dataType: "html",
            data: params
        } ).done( function( responseText ) {

            // Save response for use in complete callback
            response = arguments;

            self.html( selector ?

                // If a selector was specified, locate the right elements in a dummy div
                // Exclude scripts to avoid IE ‘Permission Denied‘ errors
                jQuery( "<div>" ).append( jQuery.parseHTML( responseText ) ).find( selector ) :

                // Otherwise use the full result
                responseText );

        // If the request succeeds, this function gets "data", "status", "jqXHR"
        // but they are ignored because response was set above.
        // If it fails, this function gets "jqXHR", "status", "error"
        } ).always( callback && function( jqXHR, status ) {
            self.each( function() {
                callback.apply( this, response || [ jqXHR.responseText, status, jqXHR ] );
            } );
        } );
    }

    return this;
};

} );

　　整个源码的工作如下：