CustomPromise.js

const CustomPromise = function(callback) {

  const res = (fn, ...args) => fn && callOnce(fn, args);
  const rej = (fn, ...args) => fn && callOnce(fn, args);

  let callOnce = (fn, args) => {
    fn.apply(null, args);
    callOnce = () => { };
  };

  this.then = function(resolve, reject) {

    reject && (this.catch = () => { });

    callback(
      res.bind(null, resolve),
      rej.bind(null, reject)
    );

    return this;
  }

  this.catch = function(reject) {
    callback(
      function() { },
      rej.bind(null, reject)
    );
  }
}

// Use Case
new CustomPromise((resolve, reject) => {
  // setTimeout(resolve, 1000, ['Date', new Date()]);
  setTimeout(reject, 1000, ['Date', new Date()]);
})
  .then(
    console.log.bind(null, 'Resolved:'),
    console.log.bind(null, 'Rejected:')
  )
  .catch(console.log.bind(null, 'Catch:'));