An example for including a JavaScript file into WordPress

example-plugin.php

<?php
/**
 * Plugin Name: Example including a JS file into WordPress.
 */

add_action( 'wp_enqueue_scripts', 'jpry_example_include_scripts' );

function jpry_example_include_scripts() {
	wp_enqueue_script(
		'jpry-example-script', // This is an arbitrary name to reference this particular script
		'https://example.com/wp-content/plugins/jpry-example/example.js', // This is the URL. For example purposes I've put the whole URL, but in WordPress, you'd usually have some other method for generating the URL for you
		array(), // An array of other script names, if any, that this script depends on. These will be loaded prior to this script
		'1.0.0', // This is a version string for browser caching purposes
	);
}

example.js

'use strict';

console.log('Successfully loaded the example.js file!');