function Animal(name) {    this.name = name        this._init()    this._add()}Animal.prototype._init = function() {    this.food = []    console.log(this.food)}Animal.prototype._add = function() {    console.log(1)    this.food.push('fish')    this.food.push('mouse')    console.log(2)}var a = new Animal('cat')執(zhí)行結(jié)果為：我的問(wèn)題是：_add方法在_init方法后執(zhí)行，為什么輸出this.food的時(shí)候已經(jīng)被賦值？想不明白，希望有人幫助我理解下b(￣▽￣)d，感謝！