手动实现bind函数

Function.prototype.myBind = function (ctx, ...rest) {
  if (typeof this !== "function") {
    throw new Error("myBind is only used to Function");
  }
  const _this = this;
  return function fn(...args) {
    // 拼接参数
    const newArgs = rest.concat(args);
    // 外部有可能 new fn();
    if (this instanceof fn) {
      return new _this(newArgs);
    }
    return this.apply(ctx, newArgs);
  };
};