How can I check for an empty/undefined/null string in JavaScript?

Question

I saw this question, but I didn\'t see a JavaScript specific example. Is there a simple string.Empty available in JavaScript, or is it just a case of checking f

Answer 1

A lot of answers, and a lot of different possibilities!

Without a doubt for quick and simple implementation the winner is: if (!str.length) {...}

However, as many other examples are available. The best functional method to go about this, I would suggest:

function empty(str)
{
    if (typeof str == 'undefined' || !str || str.length === 0 || str === "" || !/[^\s]/.test(str) || /^\s*$/.test(str) || str.replace(/\s/g,"") === "")
        return true;
    else
        return false;
}

A bit excessive, I know.