Regular Expression in java and javascript

Question

I have an regular expression built in Java.

String expr = "<a.*?id=\"(pres.*?)\".*?>Discharge.*?Medications:</a>";

I want to use same regular expression in Javascript. Will it be different or same?

It looks like you are trying to parse HTML with regex. You could just parse the string into DOM and go from there.. — Esailija
– Esailija, Commented May 15, 2012 at 15:37
Regular expressions are complicated enough on their own. If every language had different writing it would be hell! — Michael Laffargue
– Michael Laffargue, Commented May 15, 2012 at 15:37
Just have a look at regular-expressions.info/javascript.html. — Felix Kling
– Felix Kling, Commented May 15, 2012 at 15:41
Also have a look at stackoverflow.com/a/1732454/851498 . This is one of the most upvoted answers on StackOverflow. — Florian Margaine
– Florian Margaine, Commented May 15, 2012 at 15:44

Community · Accepted Answer · 2017-05-23 12:20:17Z

5

I suggest you don't do it.

Why? I will just point you out to one of the most upvoted answer on StackOverflow: https://stackoverflow.com/a/1732454/851498

In javascript, you'd better use the DOM than a regex to parse HTML.

Example:

var a = document.querySelectorAll('a');
for ( var i = 0, len = a.length; i < len; i++ ) {
    // If the id starts with "pres"
    if ( a[ i ].id.substr( 0, 3 ) === 'pres' ) {
        // check a[ i ].textContent
    }
}

Or if you're using jQuery:

$('a').each( function() {
    if ( this.id.substr( 0, 3 ) === 'pres' ) {
        // check $( this ).text()
    }
} );

I didn't code the last part, but you get the idea. Using a regex on $( this ).text() would be fine, it's not HTML.

edited May 23, 2017 at 12:20

CommunityBot

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answered May 15, 2012 at 15:51

Florian Margaine

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3 Comments

Ketan Bhavsar Over a year ago

So yeah that means... It's not good idea to use regular expression when I need to parse html right?

Florian Margaine Over a year ago

Exactly :) HTML cannot be parsed with a regex correctly, see the link for examples.

Esailija Over a year ago

@SoftwareGuruji nope especially in browsers you can easily convert a string into queryable dom. var root = document.createElement("div"); root.innerHTML = "<a id='pres'></a>"; console.log( root.firstChild.id)

Jivings · Accepted Answer · 2012-05-15 15:35:53Z

2

Not much different. Regex's in JavaScript are between /'s. So it would look like this:

var expr = /<a.*?id=\"(pres.*?)\".*?>Discharge.*?Medications:</a>/;

Edit, wrong slash. Oops.

answered May 15, 2012 at 15:35

Jivings

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1 Comment

Jivings Over a year ago

@thagorn Just noticed myself :)

mjc · Accepted Answer · 2012-05-15 15:37:32Z

2

Alternatively, you can do:

var expr = new RegExp("<a.*?id=\"(pres.*?)\".*?>Discharge.*?Medications:</a>");

For more details on RegExp in JavaScript see the MDN docs: https://developer.mozilla.org/en/JavaScript/Guide/Regular_Expressions

answered May 15, 2012 at 15:37

mjc

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Comments

RichieHindle · Accepted Answer · 2012-05-15 15:36:19Z

1

It will be the same. All the mainstream regular expression engines support the same basic syntax for regular expressions. Some add their own features on top, but your example isn't doing anything outlandish.

answered May 15, 2012 at 15:36

RichieHindle

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