these-then-this.js

One day I needed to wait on a couple async requests. I could have used: Q, Syncify.js, async.js, Step.js, or any number of other solid libraries... A dependency for just one tiny back corner of my app :(

Instead I wrote ~500 bytes that did the job. Here it is (and on GitHub):

window.these = function() {
  if( !(this instanceof these) ) { return new these( arguments ); }
  this.functions = [].concat.apply( [], [].slice.call( arguments[0] ) );
  this.results = {};
};

these.prototype.thenThis = function( cb ) {
  var instance = this, count = this.functions.length, fn;
  while( fn = this.functions.shift() ) {
    fn( function( key, value ) {
      instance.results[key] = value;
      if( !--count ) { cb( instance.results ); }
    } );
  }
  return this;
};

Install It

Copy/paste the code above into your project. Or, if you must:

bower install these-then-this

Usage

Pass functions to these as either an array or multiple arguments. Then call thenThis on the result with a callback:

these(
  function( cb ) {
    cb( 'sync', 'some' + 'sync' + 'work' );
  },
  function( cb ) {
    setTimeout( function() { cb( 'async', 'delayed' ); }, 1000 );
  }
).thenThis( function( results ) {
  alert( JSON.stringify( results, undefined, 2 ) );
} );

You can also check on the progress:

var those = these(
  function( cb ) { cb( 'quick', 1 ); },
  function( cb ) { setTimeout( function() { cb( 'slow', 2 ); }, 1000 ) }
).thenThis( function( results ) {
  alert( JSON.stringify( results, undefined, 2 ) );
} );

setTimeout( function() {
  alert(
    "quick: " + those.results.quick + ", " + // -> 1
    "slow: " + those.results.slow            // -> undefined
  );
}, 250 );

More Stuff

This was put together by Ryan Funduk on a humid afternoon. I've made lots of other things like CourseCraft, Bugrocket, jQuery-TourBus, and Mr. Password. You should subscribe to my newsletter on software development and bootstrapping for more awesome stuff like this!