Unknow identifier"List"

I’m trying to make a list of the Current Objectives in my game, I typed as I saw in another script:

var CurrentObjectives = new List.<String>();

But I am getting this error:

Assets/Scripts/UI.js(8,29): BCE0005: Unknown identifier: 'List'.

You must import generics, add this to the top of your document:

CSharp

using System.Collections.Generic;

UnityScript

import System.Collections.Generic;