Detect if number is INT or FLOAT in jquery

Question

I am currently taking input in a text-box and on-submit, I am validating the input, the input needs to be a number greater than 0, it should be integer and not contain decimal point. The problem is I am not able to find any method by which we can detect it is integer or contains decimal point. Here is the code I am using.

    txt[5] = $(this).parents('p').find('input:text').val();
    if (txt[5] == "" || isNaN(txt[5]) || txt[5] <= 0) 
    {
        alert("Incorrect Quantity");
        return false;
    }

Basically as you see I am validating the input given by user, I want to show them a message if the input is wrong, so I am currently using txt[5]%1!=0 to make sure only INT is allowed, but I am open to new answers.

Why not simply use `parseInt()`? It truncates floats and 'unparseable' input will return `NaN`. — Kiruse, Oct 20 '13 at 19:12
possible duplicate of [How to check if a number is float or integer?](http://stackoverflow.com/questions/3885817/how-to-check-if-a-number-is-float-or-integer) — Felix Kling, Oct 20 '13 at 19:13
@FelixKling: Bear in mind that the answer to that dupe will not work if the supplied argument is a string, because `typeof "5"` is `string`. — Matt Ellen, Oct 20 '13 at 19:20
@MattEllen: I don't think it's very difficult to adjust the solution. — Felix Kling, Oct 20 '13 at 19:39

score 4 · Answer 1 · answered Oct 20 '13 at 19:26

4

The simplest way is to parse the text as a Number, coerce to integer, and see if they are equal:

var numbertxt5 = Number(txt[5]);
if(numbertxt5 | 0 == numbertxt5) { /* int */
} else if (!isNaN(numbertxt5)) { /* float */
} else { /* not a number */

answered Oct 20 '13 at 19:26

SheetJS

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score 3 · Accepted Answer · edited May 23 '17 at 10:27

3

txt[5] = parseInt($(this).parents('p').find('input:text').val(), 10);

This won't validate the number (see Nirk's answer for that), but if it's not an int, it will be converted to one.

edited May 23 '17 at 10:27

Community

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answered Oct 20 '13 at 19:12

bfavaretto

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unless it's not a number – Matt Ellen Oct 20 '13 at 19:14
Yes, that will be trapped by the checks the OP already has in place. – bfavaretto Oct 20 '13 at 19:14
What is the "10" at the last? – Ankur Oct 20 '13 at 19:15
It forces the number to be parsed ad a base-10 int. Older browsers interpret numbers starting with zero as octals. @Ankur – bfavaretto Oct 20 '13 at 19:16
@MattEllen Comma, fixed – bfavaretto Oct 20 '13 at 19:18
Looking at the ', I got confused, just hold on I am just testing it. – Ankur Oct 20 '13 at 19:19
Sorry @Ankur, I'm on my ipad, touch keyboard + autocorrect causes some mistakes... – bfavaretto Oct 20 '13 at 19:21
Basically as you see I am validating the input given by user, I want to show them a message if the input is wrong, so I am currently using "txt[5]%1!=0" to make sure only INT is allowed, but I am open to new answers. – Ankur Oct 20 '13 at 19:27
Okay, I'll leave this answer as it is, since there are other answers addressing that. – bfavaretto Oct 20 '13 at 19:28

Huske · Answer 3 · 2013-10-20T19:28:13.363

That is because JavaScript has only one numerical type called number. It is neither int nor float, but it behaves like both at a time. However, you do have two methods that you can use for this parseInt and parseFloat.

var result = parseInt($(this).parents('p').find('input:text').val());
txt[5] = result;

Using parseFloat is similar. Eg.

var result = parseFloat($(this).parents('p').find('input:text').val());
txt[5] = result;

The second example is not what you want but it is here just for your reference.

UPDATE: @bfavaretto made a good point with using radix which I omitted in parseInt. Have a look at this page for reference http://www.w3schools.com/jsref/jsref_parseint.asp

Detect if number is INT or FLOAT in jquery

3 Answers3