function parseInt(string, radix, guard) {
      // Firefox < 21 and Opera < 15 follow ES3 for `parseInt`.
      // Chrome fails to trim leading <BOM> whitespace characters.
      // See https://code.google.com/p/v8/issues/detail?id=3109 for more details.
      if (guard ? isIterateeCall(string, radix, guard) : radix == null) {
        radix = 0;
      } else if (radix) {
        radix = +radix;
      }
      string = trim(string);
      return nativeParseInt(string, radix || (reHasHexPrefix.test(string) ? 16 : 10));
    }
Converts `string` to [snake case](https://en.wikipedia.org/wiki/Snake_case).

@static
@memberOf _
@category String
@param {string} [string=''] The string to convert.
@returns {string} Returns the snake cased string.
@example

_.snakeCase('Foo Bar');
// => 'foo_bar'

_.snakeCase('fooBar');
// => 'foo_bar'

_.snakeCase('--foo-bar');
// => 'foo_bar'