http://jsfiddle.net/Brj8m/

var propName = valuePropNames[i];
    if (props[propName] == null) {
      continue;
    }
    if (props.multiple) {
      warning(
        Array.isArray(props[propName]),
        'The `%s` prop supplied to <select> must be an array if ' +
        '`multiple` is true.%s',
        propName,
        getDeclarationErrorAddendum(owner)
      );
    } else {
      warning(
        !Array.isArray(props[propName]),
        'The `%s` prop supplied to <select> must be a scalar ' +
        'value if `multiple` is false.%s',
        propName,
        getDeclarationErrorAddendum(owner)
      );
    }
  }
}
/**
 * @param {ReactDOMComponent} inst
 * @param {boolean} multiple
 * @param {*} propValue A stringable (with `multiple`, a list of stringables).
 * @private
 */
function updateOptions(inst, multiple, propValue) {