JavaScript Calculation Help (Multiplying Time)

Question

I have some code that I was using to generate a calculation from two inputs but am having trouble generating the result I need.

I have two inputs (let's call them input1 and input 2). When you enter in a value, it calculates it based on the following:

(input1 x 0.156$) x ( (input2 x 15 seconds) x 4.2) x 12 months

My original code is as follows:

var calculation = function() {
  var input1 = document.getElementById('people').value;
  var input2 = document.getElementById('stories').value;
  var result = Math.floor(input1 * 0.2 * input2 * 30);
  document.getElementById('result').innerHTML = result;
  return false;
}

It's the var result that I'm having difficulty changing (the code above was for a different calculation). Any help would be greatly appreciated!

The code looks fine to me, but how are you calling this function? — Niet the Dark Absol, May 18 '16 at 14:19
technically it works but it's a different calculation than what I need now. I tried var result = Math.floor(input1 * 0.2 * (input2 * 30) * 4.2 ) * 12; but it spits out a very large result, so I think it's incorrect. — Freddy, May 18 '16 at 14:22
Well your "new" calculation is basically adding an extra `* 4.2 * 12` to the mix, making roughly a 50x increase to the previous number... — Niet the Dark Absol, May 18 '16 at 14:26
I noticed that, too. I clarified in the thread below a little more specifically what I'm trying to achieve. — Freddy, May 18 '16 at 14:39

Vladimir Drenovski · Accepted Answer · 2016-05-18T22:49:25.230

0

It looks to me that you are not implementing your formula correctly, try changing it to:

var result = Math.floor((input1 * 0.156) * ((input2 * 15)*4.2)*12);

It also will be good to tell us what 4.2 stands for.

Here's a working JSFiddle

edited May 18 '16 at 22:49

answered May 18 '16 at 14:24

Vladimir Drenovski

300
2
10

Multiplications are commutative, meaning *it doesn't matter* what order they're in. `Math.floor(input1 * 0.156 * input2 * 15 * 4. * 12)` will be just the same. – Niet the Dark Absol May 18 '16 at 14:27
The 4.2 is meant to be 4.2 weeks and the 12 = months. – Freddy May 18 '16 at 14:28
I figured out how stupid i was being the moment i clicked save edit, i removed it now ^_^ – Vladimir Drenovski May 18 '16 at 14:29
so 15 second * 4.2 weeks * 12 months = 756 what? some more explanation on what are you trying to achieve might help. – Vladimir Drenovski May 18 '16 at 14:31
Apologies. OK, here's what I'm going for..(input1 x $0.156) x ((input2) x 15 seconds) x 4.2 weeks) x 12 months = result – Freddy May 18 '16 at 14:33
@Freddy But you already have that - remember that multiplications can be in any order. – Niet the Dark Absol May 18 '16 at 14:43
Ok gimme a moment and i'll look into it, do you have any test cases ? – Vladimir Drenovski May 18 '16 at 16:48
Much appreciated! I don't have any test cases, though. – Freddy May 18 '16 at 16:54
I've updated my answer with a working JSFiddle hope that satisfies your needs. – Vladimir Drenovski May 18 '16 at 17:07
@VladimirDrenovski Fantastic! Thank you! Sorry to be a mooch here at this point, but can the result use commas (50,000 instead of 50000)? Cheers! – Freddy May 18 '16 at 19:54
I have updated the JSFiddle and it format's it as you want, but make sure to read http://stackoverflow.com/questions/149055/how-can-i-format-numbers-as-money-in-javascript regarding browser supportability. I hope to have satisfied you :) also sorry for the late answer :) – Vladimir Drenovski May 18 '16 at 22:50
@VladimirDrenovski Thanks so much! You rock! – Freddy May 19 '16 at 13:42

Umar Waliyullah · Answer 2 · 2016-05-18T14:27:39.560

0

Try this: var result = Math.floor((parseInt(input1) * 0.2) * (parseInt(input2) * 30));

by converting the input1 & input2 to numeric

edited May 18 '16 at 14:27

answered May 18 '16 at 14:25

Umar Waliyullah

529
6
17

Multiplication does that already, and the second argument to `parseInt` is NOT OPTIONAL. – Niet the Dark Absol May 18 '16 at 14:27

JavaScript Calculation Help (Multiplying Time)

2 Answers2