// 实现bind
Function.prototype._bind = function (newThis, ...bRet) {
// 原来函数的this，这里是fn
let oldThis = this
return function (...rRet) {
return oldThis.apply(newThis, [...bRet, ...rRet])
}
}
function fn() {
console.log(this) // fn
console.log(arguments) // Arguments(4) [1, 2, 4, 6, callee: ƒ, Symbol(Symbol.iterator): ƒ]
}
// 如果传null，则不改变this的指向
let newFn = fn._bind(null, 1, 2);
newFn(4, 6)
