Javascript use bitwise or equals operator |= for polyfill creation?

Question

Is there anything wrong with creating polyfills using JavaScript's bitwise¹ or equals operator |=?

Date.now |= function() {
    return +new Date;
};

¹Bitwise operator reference
²Date.now() reference

Answer 1

Um, yes? There's a major difference between | and ||, and polyfills should use:

Date.now = Date.now || function() {return +new Date;};

After all, if you used this:

Date.now = Date.now | function() {return +new Date;};

You'd get the result 0 overwriting the function.