// _bind.js
// 别人写法
Function.prototype._bind1 = function (context, ...args) {
    if (!context || context === null) context = window;
    const fn = Symbol();
    context[fn] = this;
    const _this = this;
    const result = function (...innerArgs) {
        if (this instanceof _this) {
            this[fn] = _this;
            this[fn](...[...args, ...innerArgs]);
            delete this[fn];
        } else {
            context[fn](...[...args, ...innerArgs]);
            delete context[fn];
        }
    };
    result.prototype = Object.create(this.prototype);
    return result;
};

// 官方写法
Function.prototype._bind2 = function () {
    const _this = this;
    const realThis = arguments[0] ? arguments[0] : window;
    const restParams = arguments && arguments.slice(1);
    if (typeof _this !== ‘function‘) {
        throw new TypeError(‘Function.prototype.bind - ‘ + ‘what is trying to be bound is not callable‘);
    }
    return function () {
        _this.call(realThis, ...restParams);
    };
};

手写bind