fewlines-education/fwl-readline

readline

Fewlines Readline

This package uses the NodeJs Readline and wrap it in a custom package in order to simplify its use and testing with jest mocks in Typescript.

Usage

fwl-readline is not yet available on npm. To install it, add this in your package.json file:

Installation

"dependencies": {
  "fwl-readline": "fewlines-education/fwl-readline#master"
}

Import

// example.js
import * as readline from "fwl-readline";

Create a reader

We decided to simplify the initial API of the readline package. For this reason, we only export the createInterface function.

This function takes an object parameter with two keys:

• input: generally the process.stdin
• output: generally the process.stdout

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

Type

In the example above, the created rl will have the Reader type:

interface Reader {
  question: (query: string, callback: (answer: string) => void) => void;
  close: () => void;
}

Use the created reader

rl.question("Enter something\n> ", (input) => {
  console.log(`User input: "${input}"`);
  rl.close();
});

This example will output:

Enter something
> something
User input: "something"

Mock with jest

jest.mock("fwl-readline", () => {
  return {
    createInterface: () => {
      return {
        question: () => {},
        close: () => {},
      };
    },
  };
});

import functionThatUseFwlRealine from "wherever-you-want"

// [...]

This way, the reader won't interfer when you start tests with jest.