Custom Promise Implementation

MPromise.js

function MPromise(executor) {
  this.status = "PENDING";
  this.value = null;
  this.then = (
    onFulfill = _ => _,
    onReject = _ => {
      throw _;
    }
  ) =>
    new MPromise((res, rej) => {
      try {
        let handle = this.status === "SUCCESS" ? onFulfill : onReject;
        res(handle(this.value));
      } catch (_) {
        rej(_);
      }
    });

  this.catch = onReject => this.then(undefined, onReject);

  setTimeout(() =>
    executor(
      value => {
        this.value = value;
        this.status = "SUCCESS";
      },
      value => {
        this.value = value;
        this.status = "ERROR";
      }
    )
  );
  return this;
}

// MPromise.resolve = _ => new MPromise((res, rej) => res(_));
// MPromise.reject = _ => new MPromise((res, rej) => rej(_));

// MPromise.resolve(5)
//   .then(_ => _ * 10)
//   .then(_ => {
//     throw 2;
//   })
//   .then(_ => console.log("thenable", _), e => console.error(e))
//   .then(_ => console.log("done"));

let a = new MPromise((res, rej) => {
  console.log("A");
  setTimeout(() => console.log("B"));
});
console.log("C");