Escape unsafe characters in javascript.

escape_utf8.js

/*
 * Convert unicode characters to safe characters.
 *
 * Usage:
 *  $ node
 *  > var utf8 = require("./escape_utf8.js");
 *  > utf8.unicodeEscapeChars("This is a test with æøå and ÆØÅ");
 *  'This is a test with \\xe6\\xf8\\xe5 and \\xc6\\xd8\\xc5'
 */
exports.unicodeEscapeChars = function(str) {
    var code, pref = {1: '\\x0', 2: '\\x', 3: '\\u0', 4: '\\u'};
    var escaped = str.replace(/\W/g, function(c) {
        return (pref[(code = c.charCodeAt(0).toString(16)).length] + code);
    });
    return escaped.replace(/\\x20/g," ");
};