Run function in script from command line (Node JS)

Question

I\'m writing a web app in Node. If I\'ve got some JS file db.js with a function init in it how could I call that function from the command line?

Answer 1

If your file just contains your function, for example:

myFile.js:

function myMethod(someVariable) {
    console.log(someVariable)
}

Calling it from the command line like this nothing will happen:

node myFile.js

But if you change your file:

myFile.js:

myMethod("Hello World");

function myMethod(someVariable) {
    console.log(someVariable)
}

Now this will work from the command line:

node myFile.js

Answer 2

I do a IIFE, something like that:

(() => init())();

this code will be executed immediately and invoke the init function.

Answer 3

simple way:

let's say you have db.js file in a helpers directory in project structure.

now go inside helpers directory and go to node console

 helpers $ node

2) require db.js file

> var db = require("./db")

3) call your function (in your case its init())

> db.init()

hope this helps

Answer 4

Update 2020 - CLI

As @mix3d pointed out you can just run a command where file.js is your file and someFunction is your function optionally followed by parameters separated with spaces

npx run-func file.js someFunction "just some parameter"

That's it.

file.js called in the example above

const someFunction = (param) => console.log('Welcome, your param is', param)

// exporting is crucial
module.exports = { someFunction }

More detailed description

Run directly from CLI (global)

Install

npm i -g run-func

Usage i.e. run function "init", it must be exported, see the bottom

run-func db.js init

or

Run from package.json script (local)

Install

npm i -S run-func

Setup

"scripts": {
   "init": "run-func db.js init"
}

Usage

npm run init

Params

Any following arguments will be passed as function parameters init(param1, param2)

run-func db.js init param1 param2

Important

the function (in this example init) must be exported in the file containing it

module.exports = { init };

or ES6 export

export { init };

Answer 5

Simple, in the javascript file testfile.js:

module.exports.test = function () {
   console.log('hi');
};
this.test();

Running at the prompt:

node testfile.js