index.js

/**
 * Global Names
 */

var globals = /\b(this|Array|Date|Object|Math|JSON)\b/g;

/**
 * Return immediate identifiers parsed from `str`.
 *
 * @param {String} str
 * @param {String|Function} map function or prefix
 * @return {Array}
 * @api public
 */

module.exports = function(str, fn){
  var p = unique(props(str));
  if (fn && 'string' == typeof fn) fn = prefixed(fn);
  if (fn) return map(str, p, fn);
  return p;
};

/**
 * Return immediate identifiers in `str`.
 *
 * @param {String} str
 * @return {Array}
 * @api private
 */

function props(str) {
  return str
    .replace(/\.\w+|\w+ *\(|"[^"]*"|'[^']*'|\/([^/]+)\//g, '')
    .replace(globals, '')
    .match(/[$a-zA-Z_]\w*/g)
    || [];
}

/**
 * Return `str` with `props` mapped with `fn`.
 *
 * @param {String} str
 * @param {Array} props
 * @param {Function} fn
 * @return {String}
 * @api private
 */

function map(str, props, fn) {
  var re = /\.\w+|\w+ *\(|"[^"]*"|'[^']*'|\/([^/]+)\/|[a-zA-Z_]\w*/g;
  return str.replace(re, function(_){
    if ('(' == _[_.length - 1]) return fn(_);
    if (!~props.indexOf(_)) return _;
    return fn(_);
  });
}

/**
 * Return unique array.
 *
 * @param {Array} arr
 * @return {Array}
 * @api private
 */

function unique(arr) {
  var ret = [];

  for (var i = 0; i < arr.length; i++) {
    if (~ret.indexOf(arr[i])) continue;
    ret.push(arr[i]);
  }

  return ret;
}

/**
 * Map with prefix `str`.
 */

function prefixed(str) {
  return function(_){
    return str + _;
  };
}