Unicode Escape Non-ascii Chars?

I'm looking for a function that will convert non-ascii characters to unicode escaped string.For example, "あ" => "u3042".A similar piece of code is below. However, it convert strings to "\uxxxx" instead of "uxxxx". Changing "\" to "" in code below still won't work because that result in 'u' + 'xxxx' which print as "uxxxx".I have been searching for a few days already, and start wondering if this is at all possible. ; (

Code:
var unicodeEscape = function(str) {
var code, pref = {1: '\x0', 2: '\x', 3: '\u0', 4: '\u'};

[code]....