ajax sets async to verify whether the username exists

When adding a new user, you need to determine whether the mobile phone number exists. The initial idea is very simple to set an onmouseout event on the textbox. It works well under IE, but it is not very good on Google. . This article mainly brings you an implementation method of setting up Ajax async to verify whether the user name exists. The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor to take a look, I hope it can help everyone.

ok, change your mind and check it when submitting the form:

//检验手机号码是否存在
function checkRepeat(){
	var id = '${item.id}';
	var mobile = $("#mobile").val();
	//alert(id);
	if(id==null||id==''){
		$.ajax({
			url: '/admin/adminuser/ajaxCheckReapet.shtml?mobile='+mobile,
			type: 'GET',
			dataType: 'text',
			cache:false, 
		  async:false, 
			timeout: 5000,
			error: function(){alert('数据获取失败!');},
			success: function(msg){
				if("1"==msg){
					$("#spMobile").attr("style","display:block;color:red;");
					$("#hiddenMobile").attr("value","true");
				}else{
					$("#spMobile").attr("style","display:none;");
					$("#hiddenMobile").attr("value","false");
				}
				
			}
		});
		
	}
	return true;
}


function save(){
	if(checkSImg()&&checkRepeat()){
		var hiddenMobile = $("#hiddenMobile").val();
		//alert(hiddenMobile);
		if(hiddenMobile=='false'){
			if($("#form1").form("validate")){
				$("#form1").submit();
			}
			
		}
	}
}

Then I discovered a very interesting thing in the process: when hiddenMobile returned false, the form was still submitted. I thought and thought and searched and searched, and suddenly I thought of async. Although I have never used this thing before, I guessed it and added async:false. Then I checked it. When I demonstrated it again, it actually worked

cache:false,

async:false,

Okay, let’s solve the problem, let’s study it in depth: Hum hum, there is something new, see for yourself

The default setting value of async is true. In this case, it is an asynchronous method. That is to say, when ajax sends a request, while waiting for the server to return, the foreground will continue to execute the script behind the ajax block until Success will be executed only when the server returns the correct result, which means that two threads are executed at this time, one thread after the ajax block sends the request and the script (another thread) after the ajax block

$.ajax({ 
     type:"POST", 
     url:"Venue.aspx?act=init", 
      dataType:"html", 
     success:function(result){  //function1()
       f1(); 
       f2(); 
    } 
     failure:function (result) { 
      alert('Failed'); 
     }, 
 } 
 function2();

In the above example, when the ajax block sends a request, it will stay in function1() and wait for the return from the server, but at the same time (during this waiting process), the front desk will execute function2(), In other words, two threads appear at this time, let's call them function1() and function2() here.

When asyn is set to false, the ajax request is synchronous. That is to say, after the ajax block sends a request at this time, it will wait at function1() and will not execute function2. () until the function1() part is executed.

Note

Synchronization means that when the JS code is loaded into the current AJAX, all codes in the page will stop loading and the page will go out. The state of suspended animation will be lifted when the AJAX is executed and other code pages will continue to run. Asynchronously, other codes can run while this AJAX code is running.

jquery's async:false, this attribute

Related recommendations:

Detailed example of the ajax attribute async in jQuery

Usage of async and defer in script tag

Detailed explanation of the usage of async in javascript

The above is the detailed content of ajax sets async to verify whether the username exists. For more information, please follow other related articles on the PHP Chinese website!