PromiseStuff.js

/**
 * Timeout promise that can cancel a long running promise 
 * using Promise.race
 */
 
 function timeoutPromise(delay) {
    return new Promise(function(resolve, reject) {
        setTimeout(function(){
            reject("Timeout!");
        }, delay);
    });
}
/* Whatever wins in the race, cancels others */
Promise.race([
    longRunningFunction(),
    timeoutPromise(4000)
]).then(function(result){
    console.log(result);
}).catch(function(err){
    /* Time out */
    console.log(err);
});


/**
 * Delay promise that delays resolving 
 */
function delay(time) {
 return new Promise(function(resolve, reject) {
    setTimeout(resolve, time);
 });
} 

delay(3000)
.then(function(){
  // Do something
})
.then(someOtherFunction())
.catch(function(err){   /* <-- Should always put a catch at end of a chain of promises to catch any errors */
    console.log(err);   /* as they will be swollowed otherwise */
});


/**
 * Example that uses Promise.all to fetch x amount of webpages 
 * and getting total length of them.
 */
 
 function fetch(url) {
    /* Returns a promise */
    return requestPromise(url);
 } 
 
 function addAll(...prms) {
   /* Promise.all takes a mixed array or promises
      and non promises. Its wraps the non promises in
      a promise */
    return Promise.all(prms).then(function(htmls){
      return htmls.reduce((prev, current) => {
          return current.length + prev;
      }, 0);
    });
 }
 
 function getTotal(...urls) {
    var prms = urls.map((url) => {
       return fetch(url);
    });   
   
   return addAll(...prms);
 }
 
 /* Usage */
 getTotal('http://www.google.com', 'http://www.reddit.com', 'http://www.arstechnica.com')
 .then(function(total){
    console.log(total);
 });