calculate % change in javascript

Question

var current = 12000;
var june = 14600;
var may = 11200;

I want percent change with respect to 'current' month parameter. The output should be in percent and it can add or subtract w.r.t. the current month. How to do this?

score 31 · Answer 1 · answered Jan 09 '19 at 17:35

31

Note that if one of your values is 0 you will get either -100% or Infinity%. This solves that problem:

   function percIncrease(a, b) {
        let percent;
        if(b !== 0) {
            if(a !== 0) {
                percent = (b - a) / a * 100;
            } else {
                percent = b * 100;
            }
        } else {
            percent = - a * 100;            
        }       
        return Math.floor(percent);
    }

answered Jan 09 '19 at 17:35

Daniel Usurelu

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This should be the accepted answer as it deals with the edge case scenarios. – Tushar Sharma Dec 05 '19 at 18:28
3

Why have you got `Math.floor` in there? – 1252748 Dec 04 '20 at 23:05
@1252748 it's to return the largest integer without any decimals. – user Sep 01 '22 at 01:43
percIncrease(100, 0); // -10000 – pszaba Oct 20 '22 at 17:08

score 3 · Accepted Answer · edited Jun 21 '15 at 18:49

3

Its simple maths:

var res=(current-june)/current*100.0;

edited Jun 21 '15 at 18:49

Anuj Garg

584
7
22

answered Jun 21 '15 at 17:53

Rahul Tripathi

168,305
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331

1

I think this is backwards. It gives the percentage change of the current value vs. June, rather than the other way around. – Jun 21 '15 at 18:37
@torazaburo: Agree, if comparing to current, it should be res=(x-curr)/curr, so that when x > curr, then res > 0. – Phil H Jun 24 '15 at 08:48
Right, it's backwards. However, sometimes you need to do it this way. Especially when comparing financial datas, where last quarter is "current" value. – InfiniteStack Nov 16 '22 at 22:08

score 2 · Answer 3 · answered Jun 21 '15 at 17:55

2

var percentchange = (june - current) / current * 100.0;

If your answer is a negative number then this is a percentage increase else decrease.

answered Jun 21 '15 at 17:55

Anuj Garg

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22

I tried with this. http://jsbin.com/vibofaleha/edit?html,js,output. and works perfectly fine.. – Sagar Suryawanshi Jun 21 '15 at 18:20
2

Same thing, but I'd prefer to write `(june/current - 1) * 100`. – Jun 22 '15 at 05:12

NVRM · Answer 4 · 2019-02-20T06:03:19.783

1

It isn't an easy task to handle specials cases, increase or decrease, rounding, over 100%, etc.

function calcPc(n1,n2){
  return (((n2 - n1) / n1 * 100).toLocaleString('fullwide', {maximumFractionDigits:3}) + "%");
}
   
   
   console.log(
   
     " May: "   , calcPc(11200,12000) ,
     "\nJune:" ,  calcPc(14600,12000)
   
   )

edited Feb 20 '19 at 06:03

answered Nov 21 '18 at 19:56

NVRM

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calculate % change in javascript

4 Answers4