Validating a percentage variable. No decimal points, No negative numbers

Question

This sounds easy but unable to get it to work. I need to accept a percentage number from 0 to 100 with no decimal numbers, no negative numbers. How can I do this validatation?

if ((Pcomplete == "" ) || (Pcomplete < 0 && Pcomplete > 100)) {
  alert('Percentage field is required. You need to type a number between 0 and 100');
  return false;
}

Pcomplete can never be less than 0 and greater than 100 at the same time — mplungjan, Jun 24 '16 at 12:47

Mathijs Segers · Answer 1 · 2016-06-24T12:50:30.483

5

this will always validate what you want, of course assuming it's a string when provided. Othwerise do value = "" + value or smth.

if (/[0-9]/.test(value) && parseInt(value) > 0 && parseInt(value) < 101) {
   // it IS a number, AND its value is between 0 and 100
}

Only allow numbers and only numbers between 0 and -100

the regex invalidates comma and dots etc.

edited Jun 24 '16 at 12:50

answered Jun 24 '16 at 12:48

Mathijs Segers

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Of course if you want to cast it to an int other options may apply but have strange behaviour – Mathijs Segers Jun 24 '16 at 12:49

Nina Scholz · Answer 2 · 2016-06-27T08:45:47.563

3

You should change the AND to OR, because you need the range outside.

Pcomplete < 0 || Pcomplete > 100

function check(Pcomplete) {
    if (Pcomplete === "" || Pcomplete < 0 || Pcomplete > 100 || Pcomplete - Math.floor(Pcomplete)) {
        alert('Percentage field is required. You need to type a number between 0 and 100');
        return false;
    }
    return true;
}

check('');
check('-1');
check('0.5');

edited Jun 27 '16 at 08:45

answered Jun 24 '16 at 12:47

Nina Scholz

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Nice use of '+' to convert string input to int, where string is a valid integer representation :) – GrayedFox Jun 24 '16 at 12:53
1

@GrayedFox, but not necessary here. strings became numbers with nonstrict comparisons. – Nina Scholz Jun 24 '16 at 13:29
True. I'm so used to using strict comparisons :) I just noticed, this answer won't catch floating point values however (would need a modulo check for that - example in accepted answer). – GrayedFox Jun 27 '16 at 08:26
For those interested in performance comparisons between `Math.floor` and `% 1 !== 0` using varied data sets see https://jsfiddle.net/h4kdujkk/. You'll need to be running Chrome, check the console. – GrayedFox Jun 27 '16 at 15:25

kittenchops · Accepted Answer · 2016-06-24T13:03:09.847

3

A Mod check will work to make sure that the variable is a whole number:

If Pcomplete % 1 == 0, then it is not a decimal number. Also, the vairbale cannot be both over 100 and less than 0, so seperate them with a ||.

if ((Pcomplete == "" ) || (Pcomplete < 0) || (Pcomplete > 100) || (PComplete % 1 !==0) {
  alert('Percentage field is required. You need to type a whole number between 0 and 100');
  return false;
}

edited Jun 24 '16 at 13:03

answered Jun 24 '16 at 12:48

kittenchops

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8

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`Pcomplete < 0` would fit better i think :) – Walfrat Jun 24 '16 at 13:02

score 1 · Answer 4 · answered Jun 24 '16 at 12:59

1

Number from 0 to 100

if(number < 0 || number > 100 || Number.isNaN(number)) complain();

With no decimal numbers

if(!Number.isInteger(number)) complain();

No negative numbers: already checked

If your number was a string, convert it to a number:

number = +number;

But whitespaces will be converted to 0, so before converting check

if(number.trim() === '') complain();

answered Jun 24 '16 at 12:59

Oriol

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Everybody forgets poor `NaN` :( – Oriol Jun 24 '16 at 12:59

Rian O'Dwyer · Answer 5 · 2016-06-24T12:56:57.590

0

(Pcomplete == "" ) || (Pcomplete < 0 && Pcomplete > 100)

The value cannot be < 0 and > 100

Pcomplete == ""  || Pcomplete < 0 || Pcomplete > 100 || Pcomplete % 1 !== 0

should evaluate

edited Jun 24 '16 at 12:56

answered Jun 24 '16 at 12:47

Rian O'Dwyer

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Thanks all but what about decimal. I don't want to accept something like 25.6% – Baba Jun 24 '16 at 12:54
@kittenchops suggestion is good for that. Use the mod function. Editing now – Rian O'Dwyer Jun 24 '16 at 12:56

score 0 · Answer 6 · edited Jun 24 '16 at 12:50

0

pcomplete = parseInt(pcomplete)

if (pcomplete && (pcomplete >0 && pcomplete < 100)) {

use regex

/^[1-9]{1}[0-9]{1}$/g.test("88.88")

edited Jun 24 '16 at 12:50

mplungjan

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answered Jun 24 '16 at 12:47

Piyush.kapoor

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But that would chop off the invalid decimals – mplungjan Jun 24 '16 at 12:48
use regex one line – Piyush.kapoor Jun 24 '16 at 12:50
So basically use my answer. – Mathijs Segers Jun 24 '16 at 12:51

score 0 · Answer 7 · edited May 23 '17 at 12:14

I found a related question, took the code from here (from user Blake Regalia): How to check if a variable is an integer in JavaScript?

if(typeof data === 'number') {
    var remainder = (data % 1);
    if(remainder === 0) {
        // yes, it is an integer
    }
    else if(isNaN(remainder)) {
        // no, data is either: NaN, Infinity, or -Infinity
    }
    else {
        // no, it is a float (still a number though)
    }
}
else {
    // no way, it is not even a number
}

Simplified version:

if(typeof data==='number' && (data%1)===0) {
    // data is an integer
}

All you need to do is integrate your range validation on either of these blocks

Validating a percentage variable. No decimal points, No negative numbers

7 Answers7