• ajax执行流程1


    /*
     第一步创建ajax对象:
    	new XMLHttpRequest();
    第二步填写请求信息:
    	xhr.open('method',url,Asynchronous)
    	method(请求方式):
    		1、get通常用来获取数据,偶尔也会携带一些数据
    			(1)发送的内容显示在浏览器地址栏上。
    			(2)因为浏览器地址栏长度有限制,而get是通过url向服务器发送数据的,所以发送的数据大小会被限制。
    		2、post通常用来向服务器发送数据,偶尔也会携带一些数据到客户端。
    			(1)显示在请求头信息。
    			(2)post传输数据理论来说是没有大小限制的,post的大小限制来自于服务器。
    	url:请求文件的地址
    	Asynchronous(是否异步):
    		异步:不会等待数据请求结束继续执行下边的代码,当数据请求成功的时候,在回去进行处理。
    		同步:必须等待前边的数据请求结束才可以执行下一行代码,可能会造成页面假死。
    第三步监控请求结果
    	ajax对象下边有一个onload在数据拿到之后就会触发
    	xhr.responseText表示请求到的文本内容。
    	xhr.responseXML表示请求到的XML。
    第四步发送请求
    	xhr.send(data)
    	data发送给服务器的数据
    
     * */
    document.onclick=function(){
    	var xhr=new XMLHttpRequest();
    	xhr.open('get','1.txt',true);
    	
    	xhr.onload=function(){
    		alert(xhr.responseText);
    	}
    	xhr.send();
    }
    

    例子

    	document.onclick = function(){
    		var xhr = new XMLHttpRequest();
    
    		xhr.open('get','php/data.xml',true);
    		xhr.onload = function(){
    			var entrys = xhr.responseXML.getElementsByTagName('entry');
    
    			for(var i=0;i<entrys.length;i++){
    				var names = entrys[i].getElementsByTagName('name')[0].innerHTML;
    				console.log(names);
    			}
    		};
    		xhr.send();
    	};
    
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        <title>搜索 javascript 的结果</title>
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            <title>JavaScript</title>
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                <name>克罗克福特</name>
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                <name>Douglas Crockford</name>
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            <db:attribute name="translator">赵泽欣</db:attribute>
            <db:attribute name="translator">鄢学鹍</db:attribute>
            <db:attribute name="author">Douglas Crockford</db:attribute>
            <db:attribute name="price">35.00</db:attribute>
            <db:attribute name="publisher">电子工业出版社</db:attribute>
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            <title>JavaScript DOM编程艺术</title>
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                <name>Jeremy Keith</name>
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            <db:attribute name="translator">王建桥</db:attribute>
            <db:attribute name="translator">杨晓云</db:attribute>
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            <title>JavaScript高级程序设计</title>
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            <author>
                <name>Nicholas C. Zakas</name>
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            <db:attribute name="isbn10">7115152098</db:attribute>
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            <db:attribute name="translator">曹力</db:attribute>
            <db:attribute name="translator">张欣</db:attribute>
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            <db:attribute name="price">59.00元</db:attribute>
            <db:attribute name="publisher">人民邮电出版社</db:attribute>
            <db:attribute name="pubdate">2006年9月</db:attribute>
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        <entry>
            <id>http://api.douban.com/book/subject/1232061</id>
            <title>JavaScript 权威指南</title>
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                <name>David Flanagan</name>
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            <db:attribute name="translator">张铭泽</db:attribute>
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            <db:attribute name="author">David Flanagan</db:attribute>
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            <db:attribute name="publisher">机械工业出版社</db:attribute>
            <db:attribute name="pubdate">2003-1-1</db:attribute>
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            <title>JavaScript权威指南</title>
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                <name>弗拉纳根</name>
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            <db:attribute name="author">弗拉纳根</db:attribute>
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            <db:attribute name="publisher">机械工业</db:attribute>
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            <title>JavaScript高级程序设计(第3版)</title>
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                <name>[美] Nicholas C. Zakas</name>
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            <title>基于MVC的JavaScript Web富应用开发</title>
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                <name>麦卡劳(Alex MacCaw)</name>
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            <db:attribute name="translator">江疆</db:attribute>
            <db:attribute name="translator">陈贤安</db:attribute>
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                <name>Nicholas C.Zakas</name>
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  • 原文地址:https://www.cnblogs.com/yangxue72/p/8250336.html
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