How to find whether a particular string has unicode characters (esp. Double Byte characters)

Question

To be more precise, I need to know whether (and if possible, how) I can find whether a given string has double byte characters or not. Basically, I need to open a pop-up to

Answer 1

Here is benchmark test: http://jsben.ch/NKjKd

This is much faster:

function containsNonLatinCodepoints(s) {
    return /[^\u0000-\u00ff]/.test(s);
}

than this:

function isDoubleByte(str) {
    for (var i = 0, n = str.length; i < n; i++) {
        if (str.charCodeAt( i ) > 255) { return true; }
    }
    return false;
}