Pass parameter to Node.js application from command prompt

Pass parameter to Node.js application from command prompt.

Introduction

 

You can get command-line arguments passed to your node.js application by using process.argv. process.argv is actually an array. So if you want values, out of this array you'll either have to use a loop or you can get simply by putting array index in process.argv.

Suppose you have a node.js app. "myscript.js".

You have passed parameters as:

$node myscript.js 4

Then in the code as in line number 2 of below code, we can get the parameter value as process.argv[2].

function GetSqrt() {
    var num = process.argv[2];
    console.log(" Number is " + num + " and its square " + num * num);
}
GetSqrt();

You might be thinking, why I have given index number 2 and not 0. Actually process.argv[0] will return 'node' and process.argv[1] will return your script name as in this case myscript.js.

If you have multiple arguments to pass from the command prompt, you can create a separate method for argument parsing as like

function GetSqrt() {
   var args = ParseArguments();
   args.forEach(function(num) {

       console.log(" Number is " + num + " and its square " + num * num);
   })
}
GetSqrt();

function ParseArguments() {
   var input = [];
   var arguments = process.argv;
   arguments.slice(2).forEach(function(num) {
       input.push(num);
   });
   return input;
}

Here arguments.slice(2) will remove first two arguments(node and your application name) from arguments array