for...of¹

const numbers = [1, 3, 100, 24];
for (const item of numbers) {
  console.log(item); // 1, 3, 100, 24
}

In TypeScript, as in other languages, Array.map allows you to apply a function to each of the items on a list or array. You can either pass an existing function which will take each of the items as its input parameter (say, the existing Math.sqrt function, or one that you define).

let list = [0, 1, 2, 3]; // [0, 1, 2, 3]
list.map(Math.sqrt); // [ 0, 1, 1.414.., 1.732.. ]

Or you can also define a lambda function on-the-go.

let list = [0, 1, 2, 3]; // [0, 1, 2, 3]
list.map((value, key, all) => {
  list[key] = value * 2;
}); // [ 0, 2, 4, 6]

To import JSON into your TypeScript code, you need to add the following code to a typings file (a file with a name like *.d.ts, say, json.d.ts—but it does not necessarily need to say json)¹.

// This will allow you to load `.json` files from disk

declare module "*.json"
{ const value: any;
  export default value;
}

// This will allow you to load JSON from remote URL responses

declare module "json!*"
{ const value: any;
  export default value;
}

After doing this, you can do the following in TypeScript.

import * as graph from './data/graph.json';
import data from "json!http://foo.com/data_returns_json_response/";

You can then use graph and data as JSON objects in your TypeScript code.

I used this code to load a Dynamo JSON graph into TypeScript — just change the .dyn extension to .json and it will work with this code.