Number.sign() in javascript

Question

Wonder if there are any nontrivial ways of finding number\'s sign (signum function)?
May be shorter / faster / more elegant solutions than the obvious one

Answer 1

Should this not support JavaScript’s (ECMAScript’s) signed zeroes? It seems to work when returning x rather than 0 in the “megafast” function:

function sign(x) {
    return typeof x === 'number' ? x ? x < 0 ? -1 : 1 : x === x ? x : NaN : NaN;
}

This makes it compatible with a draft of ECMAScript’s Math.sign (MDN):

Returns the sign of the x, indicating whether x is positive, negative or zero.

• If x is NaN, the result is NaN.
• If x is −0, the result is −0.
• If x is +0, the result is +0.
• If x is negative and not −0, the result is −1.
• If x is positive and not +0, the result is +1.