Function keys

underscore.js:288–296

(obj)

  // Retrieve the names of an object's own properties.
  // Delegates to **ECMAScript 5**'s native `Object.keys`.
  function keys(obj) {
    if (!isObject(obj)) return [];
    if (nativeKeys) return nativeKeys(obj);
    var keys = [];
    for (var key in obj) if (has$1(obj, key)) keys.push(key);
    // Ahem, IE < 9.
    if (hasEnumBug) collectNonEnumProps(obj, keys);
    return keys;
  }

  // Is a given array, string, or object empty?
  // An "empty" object has no enumerable own-properties.