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, May 15 '12 at 15:37
Regular expressions are complicated enough on their own. If every language had different writing it would be hell! — Michael Laffargue, May 15 '12 at 15:37
Just have a look at http://www.regular-expressions.info/javascript.html. — Felix Kling, May 15 '12 at 15:41
Also have a look at http://stackoverflow.com/a/1732454/851498 . This is one of the most upvoted answers on StackOverflow. — Florian Margaine, May 15 '12 at 15:44

score 5 · Accepted Answer · edited May 23 '17 at 12:20

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 '17 at 12:20

Community

1
1

answered May 15 '12 at 15:51

Florian Margaine

58,730
15
91
116

So yeah that means... It's not good idea to use regular expression when I need to parse html right? – Ketan Bhavsar May 15 '12 at 15:54
Exactly :) HTML **cannot** be parsed with a regex correctly, see the link for examples. – Florian Margaine May 15 '12 at 15:55
@SoftwareGuruji nope especially in browsers you can easily convert a string into queryable dom. `var root = document.createElement("div"); root.innerHTML = ""; console.log( root.firstChild.id)` – Esailija May 15 '12 at 15:56

score 2 · Answer 2 · answered May 15 '12 at 15:35

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 '12 at 15:35

Jivings

22,834
6
60
101

@thagorn Just noticed myself :) – Jivings May 15 '12 at 15:37

score 2 · Answer 3 · answered May 15 '12 at 15:37

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 '12 at 15:37

mikeycgto

3,368
3
36
47

score 1 · Answer 4 · answered May 15 '12 at 15:36

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 '12 at 15:36

RichieHindle

272,464
47
358
399

Regular Expression in java and javascript

4 Answers4