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

To use in Codeforces

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

print(x);

Refer this submission for a sample program submission.

To run your programs locally.

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';

process.stdin.resume();
process.stdin.setEncoding('utf-8');

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();
    });
    
    main();    
});

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(); // you cannot use let on CF so use just var
    
    greeting(parameterVariable);
    greeting(line2);
}

function greeting(parameterVariable) {
    console.log('Hello, World!'); // change console.log() -> print() before submitting on codeforces.
    console.log(parameterVariable);
 // 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 proof. :)