Hi,

You can add your javascript file under module_name -> static -> src-> js folder.

you can code as like following 

odoo.define('module_name.models', function (require) {

});

and you can load the js file in the manifest

'assets': {
'web.assets_backend': [
'module_name/static/src/js/file_name.js’]
}

check this references for js file

https://www.odoo.com/documentation/16.0/developer/reference/frontend/javascript_modules.html

Hope it helps

i tried, but dosnt work, this is my code.

'assets': {

​'circulacion.assets': [

​ ​'circulacion/static/src/js/assets.js',

​            ],

        },

this is my js code

the directory is static/src/js and its name assets.js

  odoo.define('circulacion.campo_nit', function (require) {

​"use strict";

​console.log("Custom JavaScript In Circulación");

});

Also tried with this

'assets': {
	​'web.assets_backend': [
	​	​'circulacion/static/src/js/asstes.js’]
}