Convert characters for comparison

Char to UTF-16

function string_as_unicode_escape(input) {
    var output = '';
    for (var i = 0, l = input.length; i < l; i++)
        output += '\\u' + (input.charCodeAt(i) + 0x10000).toString(16).slice(1);
    return output;
}

document.write(string_as_unicode_escape('abcd'));​