Chaining Nested Promises In A Loop

I am kind of new to promises and are stuck on the following exercise. I have an array of values and I want to execute an async call on each one. In the callback, I want to execute

Solution 1:

You don't need the deferred, that's the deferred anti pattern you have there since promises chain.

Also, you have to return a promise from a .then handler if you want it to wait for it to resolve.

You can simply use a for loop:

function do(val) {

  var q = Q();
  for(var i = 0; i < val; i++){
    q = q.then(asyncCall.bind(null,i))
         .then(console.log.bind(console))
         .then(console.log.bind(console,"x"));
  }

  return q; // in case you want to chain
}

fiddle.

Note: Bind just fixates the value for the function call. In this case since the first param (the this value) is null it acts like function(fn,arg){ return function(arg){ return fn(arg); }} that is, it translates a function call to a "partial application" - for more info see the MDN docs.