整理-手写代码

bind

Function.prototype.myBind = function(thisArg) {
  if(typeof this !== 'function'){
      return;
  }
  const that = this;
  const args1 = Array.prototype.slice.call(arguments, 1);
  return function() {
      that.apply(thisArg, args1.concat(Array.prototype.slice.call(arguments)));
  };
}

blog.csdn.net/q3254421/ar…

Promise

const PENDING = 'pending'
const FULFILLED = 'fulfilled'
const REJECTED = 'rejected'
function MyPromise(executor) {
  this.status = PENDING;
  this.value = undefined;
  this.reason = undefined;
  this.onFulfilledCallbacks = [];
  this.onRejectedCallbacks = [];
  const that = this;
  function resolve(value) {
    if(that.status === PENDING){
        that.status = FULFILLED;
        that.status = FULFILLED;
        that.value = value;
        that.onFulfilledCallbacks.forEach(item => item(that.value));
    }
  }
  function reject(reason) {
    if(that.status === PENDING){
        that.status = REJECTED;
        that.status = REJECTED;
        that.reason = reason;
        that.onRejectedCallbacks.forEach(item => item(that.reason));
    }
  }
  try{
      executor(resolve, reject);
  }catch(e){
      reject(e);
  }
}
MyPromise.prototype.then = function(onFulfilled, onRejected){
  if(this.status === PENDING){
      this.onFulfilledCallbacks.push(onFulfilled);
      this.onRejectedCallbacks.push(onRejected);
  }
  return this;
}

TODO 待完善！