通过var声明的变量delete不能删除,但是它也是window的属性啊？

Question

通过var声明的变量delete不能删除,但是它也是window的属性啊？求解释

var foo = 1;

window.bar = 2;

delete foo;

delete bar;

console.log(window.foo,window.bar)//1 undefined

Answer 1

因为用var声明的变量，其属性是configurable = false的，所以不能删除。var ss = 0;console.log(Object.getOwnPropertyDescriptor(window, 'ss'));/*{    configurable: false    enumerable: true    value: 0    writable: true}*/