Parsing an Int from a string in JavaScript

Question

In JavaScript, how to parse an INT from a string which starts with a letter (such as "test[123]")? I need something that will work for the example below.

My JS:

$(document).ready(function() {

    $(':input').change( function() {
        id = parseInt($(this).attr("id"));  //fails for the data below
        alert(id);
    });
}

My generated HTML:

<select id="attribute[123]">
<!-- various options -->
</select>
<select id="attribute[456]">
<!-- various options -->
</select>

Gumbo · Accepted Answer · 2009-01-15 22:12:44Z

58

You could use a regular expression to match the number:

$(this).attr("id").match(/\d+/)

answered Jan 15, 2009 at 22:12

Gumbo

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4 Comments

Wickethewok Over a year ago

Checkmark for succinctness and readability. Thanks to all though. : )

Ben Blank Over a year ago

Note that the regex should be changed to "/[-+]?\d+/" for a more general case (to allow signed ints), but that looks unnecessary for the OP's situation.

PEZ Over a year ago

What would make it more robust is to do $(this).attr("id").match(/\[(\d+)\]/)[1] since that would allow things like "attribute7[123]"

d-_-b Over a year ago

an explanation here would be very helpful.

Joel Coehoorn · Accepted Answer · 2009-01-16 00:17:38Z

25

parseInt(input.replace(/[^0-9-]/,""),10)

edited Jan 16, 2009 at 0:17

answered Jan 15, 2009 at 22:11

Joel Coehoorn

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2 Comments

Kenan Banks Over a year ago

Interestingly, this will NOT work if given valid float literals like "1e10"

Joel Coehoorn Over a year ago

Of course it won't work for floats. The op specifically asked about ints.

Logan Serman · Accepted Answer · 2009-01-15 22:12:37Z

1

Probably just filter out the string with .replace(). If there is another way then I am unaware of it:

parseInt("attribute[123]".replace("attribute[", "").replace("]", "")));

You could probably use some Regex to put that in only one .replace(), but I'm not good with Regex so I just did it twice.

Test this in your browser with

javascript:alert(parseInt("attribute[123]".replace("attribute[", "").replace("]", "")));

Should alert 123.

answered Jan 15, 2009 at 22:12

Logan Serman

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