Validate Int Value in JavaScript

Question

I am trying to figure out how to ensure that a user enters an int into a text field with JavaScript. Currently, I have the following:

var myVal = $("#myField").val();
if (isInt(myVal)) {
  alert("Awesome!");
} else {
 alert("No Good");
}

function isInt(i) {
    if ((i != null) && (i != undefined) && (i.length > 0)) {
        alert(typeof i);
        return (typeof i == 'number' && /^-?\d+$/.test(i + ''));
    }
    return false;
}

If I enter 123 into the text field, I have noticed that the typeof i is "string". I'm not sure how to perform this kind of validation. Can someone please let me know? I was suprised I didn't have any success when I Googled this.

ThiefMaster · Accepted Answer · 2012-04-09 22:45:35Z

4

function isInt(myVal) {
    return /^[+-]?\d+$/.test(myVal);
}

edited Apr 9, 2012 at 22:45

ThiefMaster

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answered Apr 9, 2012 at 20:57

Engineer

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Comments

ThiefMaster · Accepted Answer · 2012-04-09 20:45:23Z

2

You can simply use !isNaN(+myVal) or !isNaN(parseInt(myVal, 10))

answered Apr 9, 2012 at 20:45

ThiefMaster

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4 Comments

ThiefMaster Over a year ago

You can always use parseInt if you don't like using the unary + to convert it to a number :)

Pointy Over a year ago

Also myVal == ~~myVal should work for integers up to 31 bits or so (maybe it's 32; I can't remember).

ThiefMaster Over a year ago

Depends on what the user needs. If being able to convert it to a number is enough then it is correct.

Engineer Over a year ago

"Validate Int Value in JavaScript" the title of the question. There was nothing mentioned about conversion.

Starx · Accepted Answer · 2012-04-09 20:46:29Z

0

Here is a short and sweet way

function isInt(n) {
    return !isNaN(parseFloat(n)) && isFinite(n);
}

answered Apr 9, 2012 at 20:46

Starx

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1 Comment

ThiefMaster Over a year ago

That will also accept hex numbers. Use parseInt(myVal, 10) instead. Oh, and since when are zero and negative numbers not numbers? :p

kennebec · Accepted Answer · 2012-04-09 20:57:32Z

0

If you use the modulus operator on a non-integer number or string,

either a remainder or NaN is returned.

function isInt(i) {
   return i%1===0;
}

answered Apr 9, 2012 at 20:57

kennebec

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