Use node module in another file with module.exports

 <script>

    //index.js

  // const average = require('./mod');

// console.log(average([3,5,1]));

console.log('This is a index.js file');

//now get full object..

const mod = require('./mod');

console.log(mod.avg([1,2,3]));

</script>

<script>

  /mod.js

console.log('This is a mod module');

function average(arr){

    let sum = 0;

    arr.forEach(element => {

        sum += element;      

    });

    return sum/arr.length;

}

//send data in object form.

module.exports = {

    avg :average,

    name: "Harry",

    repo: "GitHub"

};

//y object h or hum ise aise send kar skte hai.

// module.exports.name = harry ;

  </script>