Can this return true function canbetrue(x) { return x != x; }

Question

A friend asked me this question he got during a job interview

function canbetrue(x) {
return x != x;
}

Which value of param will make the above function return true ?

console.log(canbetrue(param));

@Osama you're wrong on that one, look where the ! is. If it was to return true it would be x = !x; They would have to parse NaN to return true. — , Oct 11 '18 at 10:02
Take a look at [Why is NaN not equal to NaN?](https://stackoverflow.com/questions/10034149/why-is-nan-not-equal-to-nan) — t.niese, Oct 11 '18 at 10:02
@newbie : try console.log(canbetrue(NaN)) . It will return true. — teroi, Oct 11 '18 at 10:04

score 6 · Accepted Answer · edited Oct 11 '18 at 10:07

6

NaN is what you are looking for...

function canbetrue(x) {
return x != x;
}
console.log(canbetrue(NaN));

edited Oct 11 '18 at 10:07

Sudhir Ojha

answered Oct 11 '18 at 10:01

1 Answers1