In this example, we'll use TypeScript in a mod.

1. Set your mod to TypeScript mode

Select TypeScript from the JS panel dropdown:

2. Add some TypeScript

Add the TypeScript below to your mod. A few features of TypeScript highlighted here are:

  • Line 1: Use a class definition to define general behavior
  • Line 2: Define the name attribute with the type set to string
  • Line 4: Set a default value of 0 for the distanceInMeters variable
  • Line 5: Use string interpolation to insert ${} and ${distanceInMeters}
  • Line 9: Use extends to create a class that inherits properties from the Animal class
  • Lines 11-14: Create a move function that performs an action (outputText()) and then calls the move function for the parent class with super.move()



class Animal {
  name: string;
  constructor(theName: string) { = theName; }
  move(distanceInMeters: number = 0) {
    outputText(`${} moved ${distanceInMeters}m.`);

class Snake extends Animal {
  constructor(name: string) { super(name); }
  move(distanceInMeters = 5) {

function outputText(txt) {
  var newDiv = document.createElement('div');
  newDiv.innerHTML = txt;

var sam = new Snake("Sammy the Python");


3. Result

Saving the mod will reload its preview, which should look like:

Sammy the Python moved 5m.
Sammy the Python moved 34m.

The above TypeScript is pre-compiled into "regular" ES5 JavaScript automatically, and this JavaScript is what ultimately runs in the browser when the mod is loaded.

For more about TypeScript, see the official docs

Last Updated: 7/9/2019, 9:46:07 PM