Check if a string is empty (not contains any characters)

isEmpty.js

/*
 * Ref: http://stackoverflow.com/questions/154059/how-do-you-check-for-an-empty-string-in-javascript
 */

// `str` must be a string
function isEmpty(str) {
    return !!str.length;
}

// check if the `str` is empty, null or undefined (`str` may be 0 or false)
function isEmpty(str) {
    return !str;
}

// check in `if` statement
// `str` may be a empty string, null, undefined, 0 or false
if (str) {
    // statement...
}