Asynchronous for cycle in JavaScript

Question

I need a loop that waits for an async call before continuing. Something like:

for ( /* ... */ ) {

  someFunction(param1, praram2, function(result) {

    //         


        

Answer 1

If you like wilsonpage's answer but are more accustomed to using async.js's syntax, here is a variation:

function asyncEach(iterableList, callback, done) {
  var i = -1,
      length = iterableList.length;

  function loop() {
      i++;
      if (i === length) {
        done(); 
        return;
      }
      callback(iterableList[i], loop);
  } 
  loop();
}


asyncEach(['A', 'B', 'C'], function(item, callback) {
    setTimeout(function(){
    document.write('Iteration ' + item + ' 
');
    callback();
  }, 1000);
}, function() {
  document.write('All done!');
});

Demo can be found here - http://jsfiddle.net/NXTv7/8/