ajax.js

function ajax(method, url, data, success) {   //success是一个回调函数
	var xhr = null;
	try {
		xhr = new XMLHttpRequest();
	} catch (e) {
		xhr = new ActiveXObject(‘Microsoft.XMLHTTP‘);
	}
	if (method == ‘get‘ && data) {  //url在get方式的时候是可变的；如果有data存在并且方法是get的时候
		url += ‘?‘ + data;   
	}
	xhr.open(method,url,true);
	if (method == ‘get‘) {
		xhr.send();
	} else {
		xhr.setRequestHeader(‘content-type‘, ‘application/x-www-form-urlencoded‘); //POST方式在send之前,要设置请求头，告知文档类型
		xhr.send(data);
	}
	
	xhr.onreadystatechange = function() {
		
		if ( xhr.readyState == 4 ) {
			if ( xhr.status == 200 ) {
				success && success(xhr.responseText);   //如果success存在的话就执行函数
			} else {
				alert(‘出错了,Err：‘ + xhr.status);
			}
		}
		
	}
}

oBtn.onclick = function() {
		
		ajax(‘get‘,‘getNews.php‘,‘‘,function(data) {
			var data = JSON.parse( data );  //转换
				
			var oUl = document.getElementById(‘ul1‘);
			var html = ‘‘;
			for (var i=0; i<data.length; i++) {
				html += ‘<li><a href="">‘+data[i].title+‘</a> [<span>‘+data[i].date+‘</span>]</li>‘;
			}
			oUl.innerHTML = html;
		});
		
		setInterval(function() {    //定时刷新获取数据
			ajax(‘get‘,‘getNews.php‘,‘‘,function(data) {
				var data = JSON.parse( data );
					
				var oUl = document.getElementById(‘ul1‘);
				var html = ‘‘;
				for (var i=0; i<data.length; i++) {
					html += ‘<li><a href="">‘+data[i].title+‘</a> [<span>‘+data[i].date+‘</span>]</li>‘;
				}
				oUl.innerHTML = html;
			});
		}, 1000);
	}