SOURCE

function myCall(context){
    if(typeof this !== "function"){
        throw new TypeError('error')
    }
    context = context || window
    context.fn = this
    let args = [...arguments].slice(1)
    let result = context.fn(...args)
    delete context.fn
    return result
}

function myBind(context){
    if(typeof this !== 'function'){
        throw new TypeError('error')
    }
    context = context || window
    context.fn = this
    let result = null
    if(arguments[1]){
        result = context.fn(...arguments[1])
    }else{
        result = context.fn()
    }
    delete context.fn
    return result
}