Disabling the long-running-script message in Internet Explorer

Question

I have a JavaScript function that contains a for loop that iterates so many times.
After calling this function, the IE browser displays this message:

Stop running this script?
A script on this page is causing your web browser to run slowly. If it continues to run, your computer might become unresponsive.

How can I fix this?
is there anyway I can disable this message from IE?

Answer 1

This message displays when Internet Explorer reaches the maximum number of synchronous instructions for a piece of JavaScript. The default maximum is 5,000,000 instructions, you can increase this number on a single machine by editing the registry.

Internet Explorer now tracks the total number of executed script statements and resets the value each time that a new script execution is started, such as from a timeout or from an event handler, for the current page with the script engine. Internet Explorer displays a "long-running script" dialog box when that value is over a threshold amount.

The only way to solve the problem for all users that might be viewing your page is to break up the number of iterations your loop performs using timers, or refactor your code so that it doesn't need to process as many instructions.

Breaking up a loop with timers is relatively straightforward:

var i=0;
(function () {
    for (; i < 6000000; i++) {
        /*
            Normal processing here
        */

        // Every 100,000 iterations, take a break
        if ( i > 0 && i % 100000 == 0) {
            // Manually increment `i` because we break
            i++;
            // Set a timer for the next iteration 
            window.setTimeout(arguments.callee);
            break;
        }
    }
})();

Answer 2

The unresponsive script dialog box shows when some javascript thread takes too long too complete. Editing the registry could work, but you would have to do it on all client machines. You could use a "recursive closure" as follows to alleviate the problem. It's just a coding structure in which allows you to take a long running for loop and change it into something that does some work, and keeps track where it left off, yielding to the browser, then continuing where it left off until we are done.

Figure 1, Add this Utility Class RepeatingOperation to your javascript file. You will not need to change this code:

RepeatingOperation = function(op, yieldEveryIteration) {

  //keeps count of how many times we have run heavytask() 
  //before we need to temporally check back with the browser.
  var count = 0;   

  this.step = function() {

    //Each time we run heavytask(), increment the count. When count
    //is bigger than the yieldEveryIteration limit, pass control back 
    //to browser and instruct the browser to immediately call op() so
    //we can pick up where we left off.  Repeat until we are done.
    if (++count >= yieldEveryIteration) {
      count = 0;

      //pass control back to the browser, and in 1 millisecond, 
      //have the browser call the op() function.  
      setTimeout(function() { op(); }, 1, [])

      //The following return statement halts this thread, it gives 
      //the browser a sigh of relief, your long-running javascript
      //loop has ended (even though technically we havn't yet).
      //The browser decides there is no need to alarm the user of
      //an unresponsive javascript process.
      return;
      }
    op();
  };
};

Figure 2, The following code represents your code that is causing the 'stop running this script' dialog because it takes so long to complete:

process10000HeavyTasks = function() {
  var len = 10000;  
  for (var i = len - 1; i >= 0; i--) {
    heavytask();   //heavytask() can be run about 20  times before
                   //an 'unresponsive script' dialog appears.
                   //If heavytask() is run more than 20 times in one
                   //javascript thread, the browser informs the user that
                   //an unresponsive script needs to be dealt with.  

                   //This is where we need to terminate this long running
                   //thread, instruct the browser not to panic on an unresponsive
                   //script, and tell it to call us right back to pick up
                   //where we left off.
  }
}

Figure 3. The following code is the fix for the problematic code in Figure 2. Notice the for loop is replaced with a recursive closure which passes control back to the browser every 10 iterations of heavytask()

process10000HeavyTasks = function() {

  var global_i = 10000; //initialize your 'for loop stepper' (i) here.

  var repeater = new this.RepeatingOperation(function() {

    heavytask();

    if (--global_i >= 0){     //Your for loop conditional goes here.
      repeater.step();        //while we still have items to process,
                              //run the next iteration of the loop.
    }
    else {
       alert("we are done");  //when this line runs, the for loop is complete.
    }
  }, 10);                   //10 means process 10 heavytask(), then
                            //yield back to the browser, and have the
                            //browser call us right back.

  repeater.step();          //this command kicks off the recursive closure.

};

Adapted from this source:

http://www.picnet.com.au/blogs/Guido/post/2010/03/04/How-to-prevent-Stop-running-this-script-message-in-browsers

Answer 3

In my case, while playing video, I needed to call a function everytime currentTime of video updates. So I used timeupdate event of video and I came to know that it was fired at least 4 times a second (depends on the browser you use, see this). So I changed it to call a function every second like this:

var currentIntTime = 0;

var someFunction = function() {
    currentIntTime++;
    // Do something here
} 
vidEl.on('timeupdate', function(){
    if(parseInt(vidEl.currentTime) > currentIntTime) {
        someFunction();
    }
});

This reduces calls to someFunc by at least 1/3 and it may help your browser to behave normally. It did for me !!!