Console input in TypeScript

Question

How do I take in a console input from a user in TypeScript?

For example, in Python I would use:

userInput = input("Enter name: ")

What is the equivalent in TypeScript?

Answer 1

You can use the readline node module. See readline in node documentation.

To import readline in TypeScript use the asterisk(*) character. For example:

import * as readline from 'readline';

let rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.question('Is this example useful? [y/n] ', (answer) => {
  switch(answer.toLowerCase()) {
    case 'y':
      console.log('Super!');
      break;
    case 'n':
      console.log('Sorry! :(');
      break;
    default:
      console.log('Invalid answer!');
  }
  rl.close();
});

Answer 2

TypeScript only adds optional static typing and transpilation capabilities to JavaScript. It's a purely compile-time artifact; at runtime, there is no TypeScript, which is why this question is about JavaScript, not TypeScript.

If you're talking about accepting input from the console, you're probably talking about a node.js application. In Reading value from console, interactively, the solution is to use stdin:

var stdin = process.openStdin();

stdin.addListener("data", function(d) {
    // note:  d is an object, and when converted to a string it will
    // end with a linefeed.  so we (rather crudely) account for that  
    // with toString() and then substring() 
    console.log("you entered: [" + d.toString().trim() + "]");
});

Answer 3

In the browser, you would use a prompt:

var userInput = prompt('Please enter your name.');

On Node you can use Readline:

var readline = require('readline');

var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.question("What do you think of Node.js? ", function(answer) {
  console.log("Thank you for your valuable feedback:", answer);
  rl.close();
});

Answer 4

If anyone is looking for an updated and concise version...

I'm using the 'readline' package, so start with yarn add readline or npm i readline.

First, put this in a separate file (ie "question.ts")

import {createInterface} from "readline";

const rl = createInterface({
    input: process.stdin,
    output: process.stdout
});

const question = (questionText: string) =>
    new Promise<string>(resolve => rl.question(questionText, resolve))
        .finally(() => rl.close());

export default question;

and then

import question from "./question"


const name = await question("What is your name?");

const answer = await question("Are you sure? (y/N) ")
    .then(answer => answer.toLowerCase() == 'y')