​javascript 中的delete方法为什么不加括号?

Question

function createhero(name,home,weap) { this.name = name; this.home = home; if (weap == undefined) { this.weap = 'jian' }else{ this.weap = weap; } this.skill = function(){ alert(this.name+'向敌人发动攻击'); } } var hero1  = new createhero('赵日天','断罪小学','刀');                delete hero1.name;     //为什么不写成delete(hero1.name)