Could someone explain what "process.argv" means in node.js please?

I'm currently learning node.js, and I was just curious what that meant, I am learning and could you tell me why this code does what it does:

var result = 0;

  for (var i = 2; i < process.argv.length; i++){
    result += Number(process.argv[i]);
}
  console.log(result);

I know it adds the numbers that you add to the command line, but why does "i" start with 2? I understand the for loop, so you don't have to go into detail about that.

Thank you so much in advance.

Solution 1:

Do a quick console.log(process.argv) and you'll immediately spot the problem.

It starts on 2 because process.argv contains the whole command-line invocation:

process.argv = ['node', 'yourscript.js', ...]

Elements 0 and 1 are not "arguments" from the script's point of view, but they are for the shell that invoked the script.

Solution 2:

It starts with 2 because the code will be run with

node myprogram.js firstarg secondarg

So

process.argv[0] == "node"

process.argv[1] == "myprogram.js"

process.argv[2] == "firstarg"

Online docs

Solution 3:

Your program prints the sum of the numerical values of the "command line arguments" provided to the node script.

For example:

$ /usr/local/bin/node ./sum-process-argv.js 1 2 3
6

From the Node.js API documentation for process.argv:

An array containing the command line arguments. The first element will be 'node', the second element will be the name of the JavaScript file. The next elements will be any additional command line arguments.

In the above examples those values are:

process.argv[0] == '/usr/local/bin/node'
process.argv[1] == '/Users/maerics/src/js/sum-process-argv.js'
process.argv[2] == '1'
process.argv[3] == '2'
process.argv[4] == '3'

See also the Number(...) function/contructor for JavaScript.

Solution 4:

In the node.js, the command line arguments are always stored in an array. In that array, the first element is the node command we refer to because we begin the command line with word “node”. The second element is the javascript (JS) file we refer to that often comes after the node command.

As we know, in the first element in JS array begins from zero, the second element is 1, and it goes 2, 3, 4 and on. Let’s name this array process.argv and add command line arguments x and y. Then, this is how we are going to call these elements:

var process.argv = ['node', 'file.js', ‘x’, ‘y’];
var process.argv [0] = node;
var process.argv [1]= file.js;
var process.argv[2] = x;
var process.argv[3] = y;

In short, element 0 and 1 are native to node.js, and we don't use them when we write any command line argument. That's why we ignore 0 and 1 and always begin from 2.

If we want to loop through the command line arguments, again we have to start from 2. Here is what we use for looping.

for (i = 2; i < process.argv.length; i++){
console.log(process.argv[i]);
}

Solution 5:

When you execute it like:

node code.js <argument> <argument>....

It take into account all command line invocation. For process.argv[] array will have ["node","code.js","<argument>",...]
Because of that your arguments that in array start with index 2