promise_impl.js

function Promise(func) {
  var state = 'pending';
  var deferred = null; // the "then" handler
  var value;

  function resolve(newValue) {
    state = 'resolved';
    value = newValue;
    if (deferred) {
      handle(deferred);
    }
  }

  function reject(reason) {
    state = 'rejected';
    value = reason;
    if (deferred) {
      handle(deferred);
    }
  }

  function handle(handler) {
    if (state === 'pending') {
      deferred = handler;
      return;
    }


  }

  this.then = function () {

  }

  func(resolve, reject);
}