JS math causing total sum to be negative

Question

I am trying to develop a game.

However my math is a problem. Every time the total profit value goes into negative value.

How can i fix it?

var gameProfit = 10000;
var tinyOwned = 0;
var tinyCost = 10000;
var tinyIncome = 0;

function buyTiny(){
 if (gameProfit >= tinyCost){
  
  tinyOwned += 1;
  document.getElementById('tiny-owned').innerHTML = tinyOwned;
  document.getElementById('current-profit').innerHTML = "Profit : $ " + (gameProfit -= tinyCost * tinyOwned);
  document.getElementById('tiny-cost').innerHTML = "Next Cost : $ " + (tinyCost * tinyOwned + 10000);
  document.getElementById('tiny-income').innerHTML = "Income : $ " + (tinyIncome = 15000 * tinyOwned); 
 }
}

var timer = 0;
var timeInterval = 10;

window.setInterval(function gameTimer() {
 if (timer >= 0) {
  timer++;
  document.getElementById('timer-value').style.width = timer + "px";
 }
 if (timer >= 600) {
  timer = 0 + 1;
  document.getElementById('timer-value').style.width = "0px";
  
  tinyIncome = 15000 * tinyOwned;
  gameProfit += tinyIncome;
  
  document.getElementById('current-profit').innerHTML = "Profit : $ " + (gameProfit);
  
 }
}, timeInterval);

Can anyone see the problem in my code? gameProfit Variable goes into negative how to fix this?

At first if you call the function buyTiny with the value you show us : gameProfit (10 000) = gameProfit (10 000) - tinyCost(10 000) * 1 = 0 So after the first call gameProfit is 0 But i can't find where you call this function — PaulDennetiere, Oct 17 '17 at 12:28
In buyTiny() you have gameProfit -= tinyCost * tinyOwned. After first time your profit is 0. — maximelian1986, Oct 17 '17 at 12:29
And your interval is 10 ms. May be you want to set it for 1 sec or something else? — maximelian1986, Oct 17 '17 at 12:32
yes the profit must be 0 at the first call then after every function gameTimer() call the profit must increase by interval — Cornelius Labuschagne, Oct 17 '17 at 12:32
my problem is that when the tinyBuy function is called it can make gameProfit go into engative. — Cornelius Labuschagne, Oct 17 '17 at 12:33

Joel Harkes · Accepted Answer · 2017-10-17T12:35:40.657

You allow someone to buy when: gameProfit >= tinyCost

But you reduce gameProfit like: gameProfit -= tinyCost * tinyOwned

So you take more then you initially check! to fix:

if (gameProfit >= tinyCost * tinyOwned){

The math looks really messy especially since it is mixed up with setting InnerHtml. I strongly advice to first do the math and then update the Html.InnerHTML

Offtopic: make sure you escape your data if you are ever going to make it to a multiplayer game, else people can crosside script it (Can I escape html special chars in javascript?) but this is something you don't really have to worry about at this stage.

so first do the math and then add it to html – Cornelius Labuschagne Oct 17 '17 at 12:35 — Cornelius Labuschagne, Oct 17 '17 at 12:35

JS math causing total sum to be negative

1 Answers1