How do I make a upgrade for a game

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Javascript

CSS

HTML

Ok, so i want to make a clicker and i can figure it out just not upgrades like: clicking power, money per second and stuff like that so i can make a counter i can style everything i know how to use variables but i NEED the upgrades.

What I have tried:

i have tried to use "document.getElementById().onclick = function enoughtCoins?(){

if(counterVal>=10){
decreaseCounter ()counterVal=CounterVal-10
alert("purchased")"
but what that does is it multiplies the price everytime you click it and i don't want that