• MDN : JavaScript Operator - delete

delete (变量)
delete 变量

括号是可以省略的。

delete操作符用于删除定义的变量、或者删除对象中的属性。

var x = 5;
delete x;
x++; //ReferenceError: x is not defined

var x = {a: 10, b: false, c: '男'};
delete x.c;
x.c; //undefined