Function.prototype.myCall = function (ctx, ...args) {
  if (ctx === null)
    ctx = window;
  else if (typeof ctx !== 'object')
    ctx = new Object(ctx);
  const fn = Symbol();
  ctx[fn] = this;
  const rst = ctx[fn](...args);
  Reflect.deleteProperty(ctx, fn);
  return rst;
}

Function.prototype.myApply = function (ctx, args) {
  if (ctx === null)
    ctx = window;
  else if (typeof ctx !== 'object')
    ctx = new Object(ctx);
  const fn = Symbol();
  ctx[fn] = this;
  const rst = ctx[fn](...args);
  Reflect.deleteProperty(ctx, fn);
  return rst;
}


Function.prototype.myBind = function (ctx, ...args) {
  const slef = this;
  return function (...args1) {
    return slef.apply(ctx,[...args,...args1])
  }
}


function fn (a, b) {
  console.log(this);
  return a + b;
}

const rst = fn.myCall({
  name: 'yihua'
}, 2, 3)
console.log(rst);

const rst1 = fn.myApply({
  name: 'yihua'
},[3,4])
console.log(rst1);

const fn2 = fn.myBind({name:'yihua',age:18},4)
const rst2 = fn2(5);
console.log(rst2);