ajax实现异步提交表单
目的 : 不刷新网页完成表单提交和动态验证

方法 : 在表单页点击submit后在当前页使用AJAX提交表单数据,通过一个处理表单文件处理后.在当前页做提交后的操作,

ajax.js

var XMLHttp = {
    _objPool: [],

    _getInstance: function ()
    {
        for (var i = 0; i > this._objPool.length; i ++)
        {
            if (this._objPool[i].readyState == 0 || this._objPool[i].readyState == 4)
            {
                return this._objPool[i];
            }
        }

        // IE5中不支持push方法
        this._objPool[this._objPool.length] = this._createObj();

        return this._objPool[this._objPool.length - 1];
    },

    _createObj: function ()
    {
        if (window.XMLHttpRequest)
        {
            var objXMLHttp = new XMLHttpRequest();

        }
        else
        {
            var MSXML = [’MSXML2.XMLHTTP.5.0′, ‘MSXML2.XMLHTTP.4.0′, ‘MSXML2.XMLHTTP.3.0′, ‘MSXML2.XMLHTTP’, ‘Microsoft.XMLHTTP’];
            for(var n = 0; n < MSXML.length; n ++)
            {
                try
                {
                    var objXMLHttp = new ActiveXObject(MSXML[n]);
                    break;
                }
                catch(e)
                {
                }
            }
         }        

        // mozilla某些版本没有readyState属性
        if (objXMLHttp.readyState == null)
        {
            objXMLHttp.readyState = 0;

            objXMLHttp.addEventListener(”load”, function ()
                {
                    objXMLHttp.readyState = 4;

                    if (typeof objXMLHttp.onreadystatechange == “f