Clone a function definition

gistfile1.js

function cloneFunction(functionToClone) {
    functionToClone = functionToClone.toString();
    var paramStart = functionToClone.indexOf('('),
        paramEnd = functionToClone.indexOf(')'),
        paramList = functionToClone.substr(paramStart + 1, paramEnd - paramStart - 1).split(','),
        bodyStart = functionToClone.indexOf('{'),
        bodyEnd = functionToClone.lastIndexOf('}'),
        body = functionToClone.substr(bodyStart + 1, bodyEnd - bodyStart - 1),
        len,
        idx,
        parameter,
        parameters = [];
    len = paramList.length;
    for (idx = 0; idx < len; ++idx) {
        parameter = paramList[idx].trim();
        if (parameter) {
            if (0 === idx) {
                parameters.push('var ');
            } else {
                parameters.push(',\r\n     ');
            }
            parameters.push(parameter);
            parameters.push(' = arguments[');
            parameters.push(idx);
            parameters.push(']');
        }
    }
    if (parameters.length) {
        parameters.push(';\r\n');
        body = parameters.join('') + body;
    }
    return new Function(body);
}