Ajax的小封装 get,post请求

Ajax的小封装对ajax的get请求的小封装

function Ajax() {
	var xhr =null;
	 if(window.XMLHttpRequest) {
		 xhr = new XMLHttpRequest();
	 } else {

		 xhr = new ActiveXObject("Microsoft.XMLHttp");
	 }
	 this.get=function(url,success,fail){ //get请求
		 xhr.open("GET", "1.jsp",true);
		 xhr.onreadystatechange=function(){
			if(xhr.readyState==4) {
				alert(xhr.status);
				if(xhr.status==200) {
					var txt = xhr.responseText;
					 txt = eval("("+txt+")");
					 var ch = txt.charAt(0);
						if(ch=="							var xml = xhr.responseXML;
							success(eval("("+xml+")"));
						} else if(ch=="["||ch=="{") {//json类型
							 txt = eval("("+txt+")");
							 success(txt);
						} else {//不知道直接返回

							success(txt);
						}
				} else {
					 if(fail) {
						 fail(xhr.status);
					 }
				}
			}

		 };
		 xhr.send(null);

	 };


	 this.post = function (url,param,success,fail) {//post请求
		 xhr.open("POST", "1.jsp",true);
		 xhr.onreadystatechange=function(){
			if(xhr.readyState==4) {
				alert(xhr.status);
				if(xhr.status==200) {
					var txt = xhr.responseText;
					var ch = txt.charAt(0);
					if(ch=="						var xml = xhr.responseXML;
						success(eval("("+xml+")"));
					} else if(ch=="["||ch=="{") {//json类型
						 txt = eval("("+txt+")");
						 success(txt);
					} else {//不知道直接返回

						success(txt);
					}

				} else {
					 if(fail) {
						 fail(xhr.status);
					 }
				}
			}

		 };
		 xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
		 xhr.send(param);
	 };

}