Implementing timeouts for node.js callbacks

Question

This is a typical situation in node.js:

asyncFunction(arguments, callback);

When asynFunction completes, callback

Answer 1

You could do something like this:

function ensureExecution(func, timeout) {
    var timer, run, called = false;

    run = function() {   
        if(!called) {
            clearTimeout(timer);
            called = true;
            func.apply(this, arguments);
        }   
    };

    timer = setTimeout(run, timeout);
    return run;
}

Usage:

asyncFunction(arguments, ensureExecution(callback, 1000));

DEMO

But note the following:

• The timeout is started immediately when you call ensureExecution, so you cannot cache that function reference.

• The arguments passed to the callback will differ. For example asyncFunction might pass some arguments to callback upon success, but if the function is called by the timeout, no arguments will be passed. You have to keep that it mind. You could also provide default arguments with which the function should be called in this case:

  function ensureExecution(func, timeout, args, this_obj) {
      // ...
      timer = setTimeout(function() {
          run.apply(this_obj, args);
      }, timeout);
      //...
  }