Async: false and async: true in Ajax requests, ajaxasync

Async: false and async: true in Ajax requests, ajaxasync

Example:

function test(){  var temp="00";  $.ajax({    async: false,    type : "GET",    url : 'userL_checkPhone.do',    complete: function(msg){      alert('complete');    },    success : function(data) {      alert('success');      temp=data;      temp="aa";    }  });  alert(temp);  }

CheckPhone () method in UserLAction

  public void checkPhone() throws IOException {    this.getServletResponse().setContentType("text/html; charset=UTF-8");    this.getServletResponse().setHeader("Cache-Control", "no-cache");    PrintWriter out = this.getServletResponse().getWriter();    out.print("true");  }

Async: false (true by default );

When async: false is synchronous, the Ajax request in the test () method will lock the entire browser,

Other operations can be performed only after userL_checkPhone.do is executed.

Therefore, the execution result is first alert ('success'); alert ('complete'); alert ("aa ");

When async: true, ajax requests are asynchronous. However, there is a problem: the ajax request in test () and the subsequent operations are executed asynchronously. When userL_checkPhone.do is not completed, the operation following the ajax request may have been executed,

Therefore, the result is alert ('success'); alert ('complete'); alert ("00 ");

In this way, we will find that alert ("success") and alert (temp) are almost synchronous, so temp is the initial value temp = "00", rather than temp = "aa ";

The differences between async: false and async: true in the preceding Ajax request are all the content shared by Alibaba Cloud. I hope you can give us a reference and support for the customer's house.