How to calculate the total price using javascript

Hello, friends. I Have table like
quantity size price total
1-10 large £15 changed as the quantity increase
1-10 Middle £15 ....
1-10 Smalss £15 .....

total price sum of this column


I could be able use
function QuantityChangedL(qty) {
document.getElementById ('totalL').innerHTML = qty * document.getElementById ('price').innerHTML
}......

to get the each row's total value there, but how should I make the code so that the last row's total price can change according too!

Thanks very much in advance!!

You can create a variable that keeps an incrementing value (total)... Anytime your values change, you increase/decrease the value of the totals variable accordingly.

total = total - (change)

or

total = total + (change)

Does that make sense?