Remove non-ascii characters from javascript strings

gistfile1.js

function toAscii(src) {
    var ch, str, i, result = '';
        
    // `str` should now be 'double-escaped' e.g. a newline in the
    //  original `src` should be represented by '\\n' in `str`
    str = JSON.stringify(str);

    // we start from str[1] and stop at str[-1] to
    // drop the opening and closing quote marks when
    // using JSON.stringify
    for (i = 1; i < str.length - 1; i++) {
        // May need to use a "fixed" version
        // of charCodeAt as discussed here
        // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/String/charCodeAt 
        ch = str.charCodeAt(i);  

        if (ch < 128) {
            result += str.charAt(i);
        } else {
            result += '\\u' + ch.toString(16);
        }
    }
}

function fromAscii(str) {
    return JSON.parse('"' + str + '"');
}