I want to customize my POS screen in Odoo v12 and i have a problem. I add a buttons (https://i.stack.imgur.com/s1HuZ.png) and i want to add functions, but i don't know how. I used Javascript in console browser to test that functions, but it doesn't work at all. When i clicked on "+" button, the value grew up but when i clicked to the next screen the amount value was like only the one product. The buttons i add in addons/point_of_sale/static/src/xml/pos.xml and it looks sth like that:
<button string="Click" custom="click">+</button>
<button string="Click" custom="click">-</button>
Where i can add (i think JS file) in odoo with that functionality?
