Wait for a file using Jquery

Question

I have this situation where I have to check if a file exists on the server using JQuery. I can use Jquery Ajax to do this, but I need a listener which listens on the server for the presence of the file, and if it is there, then trigger some action. To provide more sense here is an example,

client--> checks on server for file(time 0)--> not present
client--> checks on server for file(time 5)--> not present
client--> checks on server for file(time 10)--> file present--> return some message to client.

So How do I implement a listener which checks for some particular file on the server and notifies the user when it is available.

Answer 1

You can use ajax polling..means check the server at a particular interval of time .

You can use setInterval function in java script to call a particular function ..And write ajax request in that function .and if the file found , just clear the timer

Check the sample code

var timerForLoadingResult=  setInterval(checkServerForFile,4000);//call the fnction in every 4 seconds.write ajax in that function.

function checkServerForFile() {                
           $.ajax({
                type: "POST",
                cache: false,
                url: url,                   
                success: function (result) {                        
              if(check result)  //if the file is on server 
              {
                 //do something
                 clearInterval(timerForLoadingResult)        // clear timer         
              }                 
                 ; }                 
            });

        }

Answer 2

The ability to run different functions depending on the HTTP Status Code returned by the server was added in jQuery 1.5. So if the server responds with a 200 execute the function needed if file exists and if it returns a 404 execute the function required if it does not.

$.ajax({
  statusCode: {
    404: function() {
      // file not found
    },
    200: function() {
      // file found
    }
  }
});

For more info see: jQuery.ajax in the jQuery docs.

Edit: From your comments I can see that you need to keep checking until the file exists. If so just wrap the request in a function and then call that function if the file is not found. Use setTimeOut though else you will be spamming the server with connection requests.