Detailed explanation of the steps to implement POST across domains using JS

This time I will bring you a detailed explanation of the steps of the JS cross-domain POST method. What are the precautions for the JS cross-domain POST method? The following is a practical case, let's take a look.

javascript Cross-domain is a very common problem, among which jsonp is the most commonly used method, but jsonp only supports get, not post, so if you want to post some data through jsonp , the head is big.

Post is implemented by generating a form in an iframe, and returns the value to the caller through postMessage.

In the first step, we first implement a back-end code that accepts jsonp. As for what language to use for implementation, you decide for yourself.

c#The code is:

protected void Page_Load(object sender, EventArgs e)
    {
      StringBuilder sbRet = new StringBuilder();
      sbRet.Append("<script>");
      sbRet.Append(Request["jsoncallback"]);
      sbRet.Append("({");
      foreach (string k in Request.Form) {
        if (k == "jsoncallback") continue;
        sbRet.Append("&#39;"+k+"&#39;:&#39;"+Request.Form[k]+"&#39;");
      }
      
      sbRet.Append("});");
      sbRet.Append("</script>");
      Response.Write(sbRet.ToString());
      Response.End();
    }

For example, what you want to return to me is { userName:'user1', password:'pass1' } , when I call http://localhost/test When ?jsoncallback=callme

you actually return<script>callme({ userName:'user1', password:'pass1' })</script>.

The second step is to build a post test page in the local folder, such as d:\test.html

　　 　　      

The third step is to browse and click submit to see if the returned value is < ;script>callme({ userName:'user1', password:'pass1' }) means there is no problem with the back-end program.

The fourth step, we write a general code to implement the above html.

nbsp;html>

  
   <meta>
    <title>测试一哈</title>
    
     
  <script>
  //源码 开始
   function postJSONP(url, data, callback) {
    var template = &#39;<form action="{{url}}" method="post" id="form1">&#39;;   
    for (var k in data) {
     template = template
       + &#39; 　<input type="text" name="&#39;+k+&#39;" value="&#39;+data[k]+&#39;" />&#39;
    }
      template = template 
      + &#39;　　<input type="text" name="jsoncallback" value="function callback(data) { parent.postMessage(data, \&#39;*\&#39;); } callback" />&#39;
      + &#39;&#39;
      + &#39;<&#39;+&#39;script>&#39;
      + &#39;document.getElementById("form1").submit();&#39;
      + &#39;</&#39;+&#39;script>&#39;;      
   template = template.replace("{{url}}", url);      
   var p = document.createElement("p");
   p.style.display = &#39;none&#39;;  
   p.innerHTML = &#39;<iframe src="">&#39;;
   document.body.appendChild(p);   
   var ifrm = p.children[0];
   var cwin = ifrm.contentWindow;
   cwin.document.write(template);   
   window.onmessage = function(e) {
   if (callback) callback(e.data);
   }
   }
   //源码 结束  
  //使用测试
   window.onload = function() {
   postJSONP(&#39;http://localhost:59898/WebForm1.aspx&#39;, { userName: &#39;张静&#39;, password: &#39;就不告诉你&#39; }, function(data) {
    console.log(11, data);
   });
   postJSONP(&#39;http://localhost:59898/WebForm1.aspx&#39;, { 仓库: &#39;1号大仓&#39;, 面积: &#39;2万平米&#39; }, function(data) {
    console.log(22, data);
   });
  }
 </script>
  

The fifth step, security issues,

window.onmessage = function(e) {
  //可通过 e 来判断来源，并做一些安全方面的处理，此处读者自己去研究吧，可以加个 console.log(e) 看看 e 有哪些内容。
  if (callback) callback(e.data);
}

I believe you have read the case in this article After mastering the method, please pay attention to other related articles on the php Chinese website for more exciting content!

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