call apply bind about js-challenges HOT 13 OPEN

Function.prototype._call = function (obj, ...args) {
	!obj && (obj = globalThis);
	// this代表要执行的函数
	obj._fn = this;
	const res = obj._fn(...args);
	delete obj._fn;
	return res;
};

Function.prototype._apply = function (obj, args) {
	// 第二个参数必须为数组或类数组对象, 否则初始化为空对象
	const arr = [];
	for (let i = 0; i < args?.length; ++i) {
		arr.push(args[i]);
	}
	return this._call(obj, ...arr);
};

Function.prototype._bind = function (obj, ...args1) {
	!obj && (obj = globalThis);
	return (...args2) => {
        obj._fn = this;
		const res = obj._fn(...[...args1, ...args2]);
		delete obj._fn;
		return res;
	};
};

Function.prototype.myCall = function(context, ...args) {
  context = context || window;
  const fn = Symbol();
  context[fn] = this;
  const result = context[fn](...args);
  delete context[fn];
  return result;
}

Function.prototype.myApply = function(context, args) {
  context = context || window;
  const fn = Symbol();
  context[fn] = this;
  const result = context[fn](...args);
  delete context[fn];
  return result;
}

Function.prototype.myBind = function(context, ...args) {
  const self = this;
  return function(...args2) {
    return self.apply(context, args.concat(args2));
  }
}

// 该代码为上面同学提交的，虽然考虑到了边界条件，更加严谨，但是是有问题的，会使始终指向全局对象window
// 问题就出在这个箭头函数，因为箭头函数的特性，会无法获得到正确的this，即调用call的函数
//  ！！！处理方式：更改为function(){}即可
Function.prototype._myCall = (thisArg, ...args) => {
  thisArg =
    thisArg !== null && thisArg !== undefined ? Object(thisArg) : window;
  let fn = Symbol();
  thisArg[fn] = this;
  const res = thisArg[fn](...args);
  delete thisArg[fn];
  return res;
};
// 同理
Function.prototype._myapply = (thisArg, args = []) => {
  thisArg =
    thisArg !== null && thisArg !== undefined ? Object(thisArg) : window;
  let fn = Symbol();
  thisArg[fn] = this;
  const res = thisArg[fn](...args);
  delete thisArg[fn];
  return res;
};
// 同理
Function.prototype._mybind = (thisArg, ...args) => {
  let fn = this;
  return (...args) => {
    return fn._myCall(thisArg, ...args);
  };
};
//最好使用symbol进行处理一下，以及对于apply传递的数组考虑一下为空的情况

Function.prototype.myapply = function (context, args) {
  context = context || window;
  args = args || [];
  const key = Symbol();
  context[key] = this;
  const res = context[key](...args); //扩展运算符对参数进行深拷贝的浅层拷贝
  delete context[key];
  return res;
};
Function.prototype.mycall = function (context, ...args) {
  context = context || window;
  args = args || [];
  const key = Symbol();
  context[key] = this;
  const res = context[key](...args);
  delete context[key];
  return res;
};
Function.prototype.mybind = function (context, ...args) {
  let self = this;
  args = args || [];
  return function (...newargs) {
    const key = Symbol();
    context[key] = self;
    const res = context[key](...args, ...newargs);
    delete context[key];
    return res;
  };
};

Function.prototype.myCall = function (context, ...args) {
  context = context || window
  args = args || []
  const key = new Symbol()
  context[key] = this
  const res = context[key](...args)
  delete context[key]
  return res
}
Function.prototype.myApply = function (context, args) {
  context = context || window
  args = args || []
  const key = new Symbol()
  context[key] = this
  const res = context[key](...args)
  delete context[key]
  return res
}
Function.prototype.myBind = function (context, ...args) {
  let self = this
  args = args || []
  return function (...newargs) {
    const key = Symbol()
    context[key] = self
    const res = context[key](...args, ...newargs)
    delete context[key]
    return res
  }
}

Function.prototype.myCall = function(context, ...args) {
  context = (context === undefined || context === null) ? window : context
  if (Object(context) !== context) {
    context = Object(context)
  }
  context.fn = this
  const result = context.fn(...args)
  delete context.fn
  return result
}

function add(params) {
  return this.a + params
}

console.log(add.myCall(0, 2))
console.log(add.call(0, 2, 3, 4))

Function.prototype.myApply = function(context, args = []) {
  context = (context === undefined || context === null) ? globalThis : context
  if (Object(context) !== context) {
    context = Object(context)
  }
  args = args === null ? [] : args
  if (!Array.isArray(args)) {
    args = Array.from(args)
  }
  context.fn = this
  const result = context.fn(...args)
  delete context.fn
  return result
}

// test case
const array = ["a", "b"];
const elements = [0, 1, 2];
array.push.myApply(array, 0);
console.log('myApply', array);
console.log('myApply', Math.max.myApply(null, null))
console.log('apply', Math.max.apply(null, null))

Function.prototype.myBind = function (that, ...partArgs) {
  var F = this
  var Prototype = F.prototype
  var boundFunction = function bound(...newArgs) {
    var args = [...partArgs, ...newArgs]
    /**
     * 若被 new 调用时，this 为即将生成的实例 bound，走 new F(...)
     */
    return this instanceof boundFunction ? new F(...args) : F.myApply(that, args)
  }
  if (Prototype && typeof Prototype === 'object') boundFunction.prototype = Prototype
  return boundFunction
}