How can I change an HTML input value's data type to integer?

Question

I'm using jQuery to retrieve a value submitted by an input button. The value is supposed to be an integer. I want to increment it by one and display it.

// Getting immediate Voting Count down button id
var countUp = $(this).closest('li').find('div > input.green').attr('id');
var count = $("#"+countUp).val() + 1;
alert (count);

The above code gives me a concatenated string. Say for instance the value is 3. I want to get 4 as the output, but the code produces 31.

Side note: any text that comes from HTML is a string by default because HTML is, well, a string :) — Álvaro González
– Álvaro González, Commented Mar 16, 2011 at 15:11

Alnitak · Accepted Answer · 2011-03-16 15:16:24Z

22

To convert strValue into an integer, either use:

parseInt(strValue, 10);

or the unary + operator.

+strValue

Note the radix parameter to parseInt because a leading 0 would cause parseInt to assume that the input was in octal, and an input of 010 would give the value of 8 instead of 10

edited Mar 16, 2011 at 15:16

answered Mar 16, 2011 at 15:04

Alnitak

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1 Comment

EoghanM Over a year ago

There was a backwards incompatible change in EcmaScript which fixes the default-octal behaviour; any browser with a release in last 10 years or so parses it as decimal without an explicit 8 as second argument: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

Quentin · Accepted Answer · 2011-03-16 15:03:18Z

6

parseInt(  $("#"+countUp).val()  ,  10  )

answered Mar 16, 2011 at 15:03

Quentin

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2 Comments

Quentin Over a year ago

Yes. Otherwise you get results such as parseInt('010'); being 8.

Álvaro González Over a year ago

@ptamzz - Yes, it does. The default is "try to guess".

justkt · Accepted Answer · 2011-03-16 15:15:34Z

2

Use parseInt as in: var count = parseInt($("#"+countUp).val(), 10) + 1; or the + operator as in var count = +$("#"+countUp).val() + 1;

edited Mar 16, 2011 at 15:15

answered Mar 16, 2011 at 15:04

justkt

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Comments

yojimbo87 · Accepted Answer · 2011-03-16 15:07:44Z

0

There is a parseInt method for that or Number constructor.

answered Mar 16, 2011 at 15:07

yojimbo87

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Comments

Landern · Accepted Answer · 2011-03-16 18:20:09Z

0

var count = parseInt(countUp, 10) + 1;

See w3schools webpage for parseInt.

edited Mar 16, 2011 at 18:20

answered Mar 16, 2011 at 15:06

Landern

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