平时工作中经常被JavaScript跨域问题所困扰，其实有很多种解决方式，下面给大家介绍常用的几种，希望能帮助到大家：

1.jsonp解决跨域问题

客户端代码：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>jsonp-跨域</title>
<script type="text/javascript" src="resources/js/jquery-1.8.3.min.js"></script>
<script type="text/javascript">
    function callbackFn(data){
        data = typeof data != 'string' ? JSON.stringify(data) : data;
        console.log('callback:'+data);
    }
    function jsonpFn(){
        $.ajax({
            type:"get",
            dataType:"jsonp",
            url:"http://localhost:9393/ccy_server/server.jsp",
            jsonpCallback:"callbackFn",
            success:function(data){
                data = typeof data != 'string' ? JSON.stringify(data) : data;
                console.log('success.data:'+data);
            }
        });
    }
    function ajaxFn(){
        var xmlhttp = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
        var url = "http://localhost:9393/ccy_server/server.jsp";
        xmlhttp.onreadystatechange = function(){
            if(xmlhttp.readyState==4){
                if(xmlhttp.status==200){
                    callbackFn(xmlhttp.responseText);
                }
            }
        }
        xmlhttp.open('GET',url,true);
        xmlhttp.send(null);
    }
    ajaxFn();
    //jsonpFn();
</script>
</head>
<body>
</body>
</html>

服务端代码：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%
    String result = "{\"name\":\"ccy\",\"age\":18,\"info\":{\"address\":\"wuhan\",\"interest\":\"playCards\"}}";
    out.println("callbackFn("+result+")");
%>

相信大家对此种方式并不陌生，需要引用jquery库文件，并且要与服务端进行协调处理。

我先写了个简单的ajax调用非同源的异步请求直接报错

执行jsonpFn方法

成功获取服务端信息！

2.window.name解决跨域问题

在客户端浏览器中每个页面都有一个独立的窗口对象window，默认情况下window.name为空，在窗口的生命周期中，载入的所有页面共享一个window.name并且每个页面都有对此读写的权限，window.name会一直存在当前窗口，但存储的字符串不超过2M。

http://localhost:8383/ccy_client/window_name.html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>window.name-跨域</title>
<script type="text/javascript">
    window.name = "我是 window.name 字符串";
    setTimeout(function(){
        window.location = "http://localhost:9393/ccy_server/window_name.html";
    },2000);
</script>
</head>
<body>
</body>
</html>

http://localhost:9393/ccy_server/window_name.html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>window.name-跨域</title>
<script type="text/javascript">
    var str = window.name;
    console.log('ccy_server.window_name:'+str);
</script>
</head>
<body>
</body>
</html>

chrome打印信息

" data-src="https://user-gold-cdn.xitu.io/2018/12/2/1676f2f4ec55c056?imageView2/0/w/1280/h/960/format/webp/ignore-error/1" data-width="758" data-height="42" />

上面是以window.location跳转的方式获取window.name字符串信息，平时开发中经常需要异步获取，请继续往下看：

http://localhost:8383/ccy_client/window_name_iframe.html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>window.name-跨域</title>
</head>
<body>
<script type="text/javascript">
    var boo = false;
    var iframe = document.createElement('iframe');
    var loadData = function() {
        if (boo) {
            var data = iframe.contentWindow.name;    //获取window.name
            console.log(data);
            //销毁数据
            iframe.contentWindow.document.write('');
            iframe.contentWindow.close();
            document.body.removeChild(iframe);
        } else {
            boo = true;
            iframe.contentWindow.location = "";    // 设置的代理文件,iframe重新载入
        }
    };
    iframe.src = 'http://localhost:9393/ccy_server/window_name_iframe.html';
    if (iframe.attachEvent) {
        iframe.attachEvent('onload', loadData);
    } else {
        iframe.onload  = loadData;
    }
    document.body.appendChild(iframe);
</script>
</body>
</html>

http://localhost:9393/ccy_server/window_name_iframe.html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>window.name-跨域</title>
<script type="text/javascript">
    window.name = '我是 http://localhost:9393/ccy_server/window_name_iframe.html';
</script>
</head>
<body>
</body>
</html>

chrome打印信息

成功获取非同源地址的数据信息，主要是通过iframe的src属性，类似含有src属性的标签都可以成功处理跨域问题img,script

3.postMessage解决跨域问题

h5新特性，window.postMessage(msg,targetOrigin);

msg:传入的字符串信息

targetOrigin:目标源（协议主机端口有效）

同样借助iframe进行跨域操作

http://localhost:8383/ccy_client/postMessage.html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>postMessage-跨域</title>
</head>
<body>
<iframe id="ifr" src="http://localhost:9393/ccy_server/postMessage.html" style="display: none;"></iframe>
<br>
<input id="txt" type="text" style="width:600px;height:70px;"/>
<br>
<input id="btn" type="button" value="获取9393数据" onclick="getData();" style="width:180px;height:60px;"/>
<script type="text/javascript">
    var data;
    function handleMsg(e){
        e = e || event;
        data = e.data;
        console.log('8383:'+e.data);
    }
    if(window.addEventListener){
        window.addEventListener('message', handleMsg);
    }else{
        window.attachEvent('onmessage', handleMsg);
    }
    function getData(){
        document.getElementById('txt').value=data;
        var msg = 'http://localhost:8383/ccy_client/postMessage.html';
        window.frames[0].postMessage(msg, 'http://localhost:9393');
    }
</script>
</body>
</html>

http://localhost:9393/ccy_server/postMessage.html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>postMessage-跨域</title>
</head>
<body>
<script type="text/javascript">
    function handleMsg(e){
        e = e || event;
        console.log('9393:'+e.data);
    }
    if(window.addEventListener){
        window.addEventListener('message', handleMsg);
    }else{
        window.attachEvent('onmessage', handleMsg);
    }
    window.onload = function(){
        var msg = '我是 http://localhost:9393/ccy_server/postMessage.html';
        window.parent.postMessage(msg, 'http://localhost:8383');
    }
</script>
</body>
</html>

chrome打印信息