How to take input in Node.js / Javascript from file or stdin.

Revision en7, by RohitKaushal, 2020-01-03 09:18:55

How to get Input from stdin / input.txt in Node.js / JavaScript

To use in Codeforces (javascript)

readline() Reads one line from stdin.

to get some space separated values from a line:

var num = readline().split(" ").map(x => parseInt(x)); // num will be an array [1,2,3]
var x = num[0]; // to store values in different variables. 
var y= num[1];
var z= num[2];

var num2= readline(); // reads next line.

For Output


Refer this submission for a sample program submission.

To run your programs locally and use in CF (Node.js)

readline() do not work by default if you try to use it locally on your computer.

Write this header code in the beginning of your js code

'use strict';


let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;

process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();

function readline() {
    return inputString[currentLine++];

// thats all what you have to write to get input from stdin, using readLine.

// Main code runs in main();

function main() {
    const parameterVariable = readline();
    var line2 = readline(); 

function greeting(parameterVariable) {
    console.log('Hello, World!'); // change console.log() -> print() before submitting on codeforces if submitting as javascript.
 // Write a line of code that prints parameterVariable to stdout using console.log:  

Testing Locally

paste your input in a text file input.txt

then $ cat input.txt | node main.js to view on console. $ cat input.txt | node main.js > output.txt to store the output in file.

you can also make a sublime-build file for this and then just press Ctrl+B

Tools> Build System > new build system > nodejs.sublime-build { "shell_cmd": "cat $file_path/input.txt | node $file > $file_path/output.txt" }

Here is a Sample Image :)

Tags nodejs, javascript, input, stdin, codeforce javascript


  Rev. Lang. By When Δ Comment
en8 English RohitKaushal 2020-01-26 11:58:34 742 Tiny change: 'ion.**\n\n\n\n\n###T' -> 'ion.**\n\n<hr>\n\n\n###T'
en7 English RohitKaushal 2020-01-03 09:18:55 3
en6 English RohitKaushal 2019-10-17 12:19:26 7 Tiny change: 'cb52.png) proof. :)\n ' -> 'cb52.png) :)\n '
en5 English RohitKaushal 2019-09-14 19:49:10 107
en4 English RohitKaushal 2019-09-14 19:37:07 159
en3 English RohitKaushal 2019-09-08 16:55:46 882 Tiny change: 'orces\n\n```readline()``` Reads on' -> 'orces\n\n`readline()` Reads on'
en2 English RohitKaushal 2019-09-06 23:08:34 0 (published)
en1 English RohitKaushal 2019-09-06 23:07:41 1459 Initial revision (saved to drafts)