javascript - Variable delete declared through var cannot be deleted, but it is also a property of window?

Question

The variable delete declared through var cannot be deleted, but it is also a property of window? Seek to explain

var foo = 1;
window.bar = 2;
delete foo;
delete bar;
console.log(window.foo,window.bar)//1 undefined

Answer 1

Because the variable declared with var has the attribute configurable = false, so it cannot be deleted.

var ss = 0;
console.log(Object.getOwnPropertyDescriptor(window, 'ss'));

/*
{
    configurable: false
    enumerable: true
    value: 0
    writable: true
}
*/