Calling a javascript function in another js file

A function cannot be called unless it was defined in the same file or one loaded before the attempt to call it.

A function cannot be called unless it is in the same or greater scope then the one trying to call it.

You declare function fn1 in first.js, and then in second you can just have fn1();

1.js:

function fn1 () {
    alert();
}

2.js:

fn1();

index.html :

<script type="text/javascript" src="1.js"></script>
<script type="text/javascript" src="2.js"></script>

1st JS:

function fn(){
   alert("Hello! Uncle Namaste...Chalo Kaaam ki Baat p Aate h...");
}

2nd JS:

$.getscript("url or name of 1st Js File",function(){
fn();
});

You could consider using the es6 import export syntax. In file 1;

export function f1() {...}

And then in file 2;

import { f1 } from "./file1.js";
f1();

Please note that this only works if you're using <script src="./file2.js" type="module">

You will not need two script tags if you do it this way. You simply need the main script, and you can import all your other stuff there.