Assign Regex object to html input pattern

Question

I need to assign a regex object to an input element pattern attribute programmatically. Below is my current implementation:

var regex = /\d{5}/;
element.attr("pattern", regex.toString().slice(1,-1);

Is there a better way to do this without string manipulation?

Are you using the regex object for anything else? If not you can obviously just assign the string directly with element.attr("pattern","\\d{5}"). — nnnnnn
– nnnnnn, Commented Mar 19, 2013 at 3:05
RegExp instances have a source property which contains their text, so /\d{5}/.source === "\\d{5}". — Mike Samuel
– Mike Samuel, Commented Mar 19, 2013 at 3:31
@nnnnnn—there is no need to quote the backslash, \d{5} should do (and does in Firefox). — RobG
– RobG, Commented Mar 19, 2013 at 3:43
@RobG - In a string literal (as in my previous comment) you need to escape the backslash, including in FF. In a regex literal you don't escape backslashes. (I know that you know this...) — nnnnnn
– nnnnnn, Commented Mar 19, 2013 at 4:09

Mike Samuel · Accepted Answer · 2013-03-19 03:34:59Z

16

RegExp instances have a source property which contains their text:

The value of the source property is a String in the form of a Pattern representing the current regular expression.

Therefore

/\d{5}/.source === "\\d{5}"

so your code could be changed to

var regex = /\d{5}/;
element.setAttribute("pattern", regex.source);

answered Mar 19, 2013 at 3:34

Mike Samuel

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Comments

deerchao · Accepted Answer · 2013-03-19 03:06:45Z

-1

If you are using jQuery, use prop instead of attr. Becasue in newer version of jQuery, attr is readonly, prop is read/write.

element.prop('pattern', regex.toString().slice(1,-1));

edited Mar 19, 2013 at 3:06

answered Mar 19, 2013 at 3:01

deerchao

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5 Comments

nnnnnn Over a year ago

What's the .data() method? If you're going to assume jQuery you can just save the regex directly as an object...

mkoryak Over a year ago

i dont see anything wrong with this. setting a data attribute is better than setting an element attr

nnnnnn Over a year ago

@mkoryak - OP asked about the html5 pattern attribute, which actually has an effect on how the input element behaves. Changing that to a non-attribute data property doesn't help.

RobG Over a year ago

Why do you assume jQuery? It isn't a tag, nor in the question or the code.

deerchao Over a year ago

Didn't know about the "html5 pattern" attribute. Learned something.

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