Adds a timeout to a JavaScript promise, rejects if not resolved within timeout period

javascript-promise-timeout.js

/**
 * wraps a promise in a timeout, allowing the promise to reject if not resolve with a specific period of time
 * @param {integer} ms - milliseconds to wait before rejecting promise if not resolved
 * @param {Promise} promise to monitor
 * @Example
 *  promiseTimeout(1000, fetch('https://courseof.life/johndoherty.json'))
 *      .then(function(cvData){
 *          alert(cvData);
 *      })
 *      .catch(function(){
 *          alert('request either failed or timedout');
 *      });
 */
function promiseTimeout(ms, promise){

  return new Promise(function(resolve, reject){

    // create a timeout to reject promise if not resolved
    var timer = setTimeout(function(){
        reject(new Error("promise timeout"));
    }, ms);

    promise
        .then(function(res){
            clearTimeout(timer);
            resolve(res);
        })
        .catch(function(err){
            clearTimeout(timer);
            reject(err);
        });
  });
};