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

All the previous answers are good, but this will be even better. Use dual NOT operators (!!):

if (!!str) {
    // Some code here
}

Or use type casting:

if (Boolean(str)) {
    // Code here
}

Both do the same function. Typecast the variable to Boolean, where str is a variable.
It returns false for null, undefined, 0, 000, "", false.
It returns true for string "0" and whitespace " ".