Question

I have a javascript function which supposed to check whether a task is completed.
When the task is completed there is a completion record in a file on the server.
The function supposed to make recursive calls to the server with some delay (potentially increasing) till it gets the completion record in the file.
The code given below makes excessive calls to the server with interval less than a second
example from Web Console:
[20:06:21.202] [20:06:21.563] [20:06:21.990]
But the task becomes competed on variable waittime value getting equal to max_waittime .
Though for a test case overall output is as expected, something is wrong with the function.
Where I’m wrong?

 function check_status(time,div_id,filename) {

var status =0;
var waittime=time;

var max_waittime=11000000;
if (waittime < max_waittime){waittime=waittime+1000000; }

$.ajax({
  type: "GET",
  async: false,
  url: "code_on_server_checking_file.php",
  data: "f="+filename,
  dataType: "text",
  success: function(content) {

    if (content ) {
    // stuff related to output of the result 
       ....
       return status=1;
     }
    else {return status=0;}   
      }
   });

if (status == 0 && waittime < 20000000){
   setTimeout(check_status(waittime,div_id,filename),waittime);
  }
else {alert('check_status passed!'+status+'|'+waittime);}
}

Answer 1

You are calling the function instead of giving it as a reference to setTimeout. Wrap your function call in an anonymous function. Also, it would be better to simply set up the call in the ajax callback if needed rather than using a synchronous call. A synchronous call will tie up your browser.

function check_status(time,div_id,filename) {

    $.ajax({
      type: "GET",
      url: "code_on_server_checking_file.php",
      data: "f="+filename,
      dataType: "text",
      success: function(content) {
        if (content ) {
        // stuff related to output of the result 
        }
        else {
          time += 1000000;
          if (time < 20000000) {
              setTimeout( function() { check_status( time, div_id, filename); }, time );
          }
        }
      }
    });

}