Nodejs Set a global function and call a nested function - node.js

Question

My Main function
import AppLauncher from './Applauncher'
function Mainfunc() {
global.app= AppLauncher()
global.app.start('index')
}
AppLauncher.js
function AppLauncher() {
function start(opts){
console.log('functions start called with' + opts)
}
}
export default AppLauncher
I want to assign the AppLauncher function as global, and call the start function nested inside it

Answer 1

Constructors are the way to go. You can do something like this:
// AppLauncher.js
function AppLauncher() {
// run some code...
// notice `this`
this.start = function(opts) {
console.log('start function called with', opts);
}
}
export default AppLauncher;
In your main function, call it with the new keyword:
import AppLauncher from './AppLauncher';
function Mainfunc() {
global.app = new AppLauncher();
global.app.start('index');
}
Constructors can also be written as classes (you can use it the same way as in my last example):
class AppLauncher {
constructor() {
// Anything in here gets executed when once you create an object from this class with the `new` keyword
}
// Instead of `this` we add a method to the class:
start(opts) {
console.log('start function called with', opts);
}
}
export default AppLauncher;
More about constructors: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/constructor
If you don't want to use a constructor, you can also return an object:
// AppLauncher.js
function AppLauncher() {
// Some code here...
return {
start(opts) {
console.log("function start called with", opts);
}
};
}
export default AppLauncher;
And you can use this just like you thought:
import AppLauncher from `./AppLauncher`;
function Mainfunc() {
global.app = AppLauncher();
global.app.start('index');
}
As a side note, it's conventional to call constructors with PascalCase, while regular functions are called with camelCase.