javascript: html5-pattern regex question

Question

When I run this script with "\d+" as pattern value, the regex doesn't work as I expected. When I escape the backslash it works. Is the backslash the only character that I have to escape?

<!DOCTYPE HTML>
<html>
<head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8" />
</head>
<body>
<p>Enter a number:</p>
<form id="form">
    <script type="text/javascript">
        var form = document.getElementById( 'form' );
        var input = document.createElement( 'input' );
        input.name = 'amount';
        input.type = 'number';
        input.pattern = "\\d+";
        form.appendChild( input );
    </script>
    <br /><br />
    <input type="submit" value="OK"/>
</form>
</body>
</html>

ipr101 · Accepted Answer · 2011-08-27 18:22:36Z

2

You have to escape the backslash character in a string used as a RegEx expression just as you would in any JavaScript string.

To include a literal backslash inside a string, you must escape the backslash character. For example, to assign the file path c:\temp to a string, use the following:

var home = "c:\\temp";

https://developer.mozilla.org/en/JavaScript/Guide/Values,_Variables,_and_Literals#Escaping_Characters

edited Aug 27, 2011 at 18:22

answered Aug 27, 2011 at 17:50

ipr101

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6 Comments

Madara's Ghost Over a year ago

I don't think he wants to add a backslash but a number. the backlash should be escaped because it's in the string

ipr101 Over a year ago

Isn't that what I put? I don't really see the difference between my answer and your answer.

ipr101 Over a year ago

BTW - Let me know which bit of my answer you think is unclear and I'll happily change it.

Madara's Ghost Over a year ago

your block quotes requires code format. the line with the file path.

ipr101 Over a year ago

OK, fixed. I've left the code in the quote blocks to make it clear that all that content is from MDN.

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Madara's Ghost · Accepted Answer · 2011-08-27 17:53:30Z

2

the back slash must be escaped as part of the strings syntax.

answered Aug 27, 2011 at 17:53

Madara's Ghost

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2 Comments

Quentin Over a year ago

JavaScript recognises escape sequences in single quote delimited strings. Using single quotes won't help here.

Madara's Ghost Over a year ago

seems like it, I've confused with . fixed.

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