实现call、apply、bind方法

实现call方法

实现代码展示

Function.prototype.myCall = function (context, ...args) {
    if (typeof this !== 'function') {
        throw new TypeError('Call must be called on a function')
    }
    context = context || window
    const fn = Symbol('fn')
    context[fn] = this
    const result = context[fn](...args)
    delete context[fn]
    return result
}

实现apply方法

实现代码展示

Function.prototype.myApply = function (context, args) {
    if (typeof this !== 'function') {
        throw new TypeError('Apply must be called on a function')
    }
    context = context || window
    const fn = Symbol('fn')
    context[fn] = this
    const result = context[fn](...args)
    delete context[fn]
    return result
}

实现bind方法

实现代码展示

Function.prototype.myBind = function (context, ...args) {
    if (typeof this !== 'function') {
        throw new TypeError('Bind must be called on a function')
    }
    context = context || window
    const fn = Symbol('fn')
    context[fn] = this
    return function (...newArgs) {
        const result = context[fn](...args, ...newArgs)
        delete context[fn]
        return result
    }
}