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How to write regexp for finding :smile: in javascript?

I want to write a regular expression, in JavaScript, for finding the string starting and ending with :.
For example "hello :smile: :sleeping:" from this string I need to find the strings which are starting and ending with the : characters. I tried the expression below, but it didn't work:
^:.*\:$

My guess is that you not only want to find the string, but also replace it. For that you should look at using a capture in the regexp combined with a replacement function.
const emojiPattern = /:(\w+):/g
function replaceEmojiTags(text) {
return text.replace(emojiPattern, function (tag, emotion) {
// The emotion will be the captured word between your tags,
// so either "sleep" or "sleeping" in your example
//
// In this function you would take that emotion and return
// whatever you want based on the input parameter and the
// whole tag would be replaced
//
// As an example, let's say you had a bunch of GIF images
// for the different emotions:
return '<img src="/img/emoji/' + emotion + '.gif" />';
});
}
With that code you could then run your function on any input string and replace the tags to get the HTML for the actual images in them. As in your example:
replaceEmojiTags('hello :smile: :sleeping:')
// 'hello <img src="/img/emoji/smile.gif" /> <img src="/img/emoji/sleeping.gif" />'
EDIT: To support hyphens within the emotion, as in "big-smile", the pattern needs to be changed since it is only looking for word characters. For this there is probably also a restriction such that the hyphen must join two words so that it shouldn't accept "-big-smile" or "big-smile-". For that you need to change the pattern to:
const emojiPattern = /:(\w+(-\w+)*):/g
That pattern is looking for any word that is then followed by zero or more instances of a hyphen followed by a word. It would match any of the following: "smile", "big-smile", "big-smile-bigger".

The ^ and $ are anchors (start and end respectively). These cause your regex to explicitly match an entire string which starts with : has anything between it and ends with :.
If you want to match characters within a string you can remove the anchors.
Your * indicates zero or more so you'll be matching :: as well. It'll be better to change this to + which means one or more. In fact if you're just looking for text you may want to use a range [a-z0-9] with a case insensitive modifier.
If we put it all together we'll have regex like this /:([a-z0-9]+):/gmi
match a string beginning with : with any alphanumeric character one or more times ending in : with the modifiers g globally, m multi-line and i case insensitive for things like :FacePalm:.
Using it in JavaScript we can end up with:
var mytext = 'Hello :smile: and jolly :wave:';
var matches = mytext.match(/:([a-z0-9]+):/gmi);
// matches = [':smile:', ':wave:'];
You'll have an array with each match found.

REGEX - after bracket get data until end bracket

I have a string like the following:
SOME TEXT (BI1) SOME MORE TEXT (BI17) SOME FINAL TEXT (BI1234)
Question
I am trying to make a regex to get just the information between the curly brackets, for example the end string would look like:
BI1 BI17 BI1234
I have found this example on stackoverflow which will get the first value BI1, but will ignore the rest after.
Get text between two rounded brackets
this is the REGEX I created from the above link: /\(([^)]+)\)/g but it includes the brackets, I want to remove these.
I am using this website to attempt to solve this query which has a testing window to see if the regex entered works:
http://www.regexr.com
Additional Information
there can be any amount of numbers also, which is why I have given 3 different examples.
this is a continous string, not on seperate lines
thanks for any help on this matter.

While this isn't possible using just regexes, you can do it with string#split and the following regex:
\).*?\(|^.*?\(|\).*?$
Yielding code that looks a bit like this:
function getBracketed(str) {
return str.split(/\).*?\(|^.*?\(|\).*?$/).filter(Boolean);
}
(You need to filter out the empty strings that'll appear at the beginning and end if you do it this way - hence the extra operation).
Regex demo on Regex101
Code demo on Repl.it

If you need to keep all inside parentheses and remove everything else, you might use
var str = "SOME TEXT (BI1) SOME MORE TEXT (BI17) SOME FINAL TEXT (BI1234)";
var result = str.replace(/.*?\(([^()]*)\)/g, " $1").trim();
console.log(result);
If you need to get only the BI+digits pattern inside parentheses, use
/.*?\((BI\d+)\)/g
Details:
.*? - match any 0+ chars other than linebreak symbols
\( - match a (
(BI\d+) - Group 1 capturing BI + 1 or more digits (\d+) (or [^()]* - zero or more chars other than ( and ))
\) - a closing ).
To get all the values as array (say, for later joining), use
var str = "SOME TEXT (BI1) SOME MORE TEXT (BI17) SOME FINAL TEXT (BI1234)";
var re = /\((BI\d+)\)/g;
var res =str.match(re).map(function(s) {return s.substring(1, s.length-1);})
console.log(res);
console.log(res.join(" "));

comparing and replacing using regex in javascript : leaving a word in between

I am trying to replace a pattern as below:
Original :
welocme
Need to be replaced as :
welcome
Tried the below approach:
String text = "welocme";
Pattern linkPattern = Pattern.compile("a href=\"#");
text = linkPattern.matcher(text).replaceAll("a href=\"javascript:call()\"");
But not able to add the idvalue in between. Kindly help me out.
Thanks in advance.

how about a simple
text.replaceAll("#idvalue","javascript:call('idvalue')")
for this case only. If you are looking to do something more comprehensive, then as suggested in the other answer, an XML parser would be ideal.

Try getting the part that might change and you want to keep as a group, e.g. like this:
text = text.replaceAll( "href=\"#(.*?)\"", "href=\"javascript:call('$1')" );
This basically matches and replaces href="whatever" with whatever being caught by capturing group 1 and reinserted in the replacement string by using $1 as a reference to the content of group 1.
Note that applying regex to HTML and Javascript might be tricky (single or double quotes allowed, comments, nested elements etc.) so it might be better to use a html parser instead.

Add a capture group to the matcher regex and then reference the group in the replacemet. I found using the JavaDoc for Matcher, that you need to use '$' instead of '\' to access the capture group in the replacement.
Code:
String text = "welcome";
System.out.println("input: " + text);
Pattern linkPattern = Pattern.compile("a href=\"#([^\"]+)\"");
text = linkPattern.matcher(text).replaceAll("a href=\"javascript:call('$1')\"");
System.out.println("output: " +text);
Result:
input: welcome
output: welcome

regex encapsulation

I've got a question concerning regex.
I was wondering how one could replace an encapsulated text, something like {key:23} to something like <span class="highlightable">23</span, so that the entity will still remain encapsulated, but with something else.
I will do this in JS, but the regex is what is important, I have been searching for a while, probably searching for the wrong terms, I should probably learn more about regex, generally.
In any case, is there someone who knows how to perform this operation with simplicity?
Thanks!

It's important that you find {key:23} in your text first, and then replace it with your wanted syntax, this way you avoid replacing {key:'sometext'} with that syntax which is unwanted.
var str = "some random text {key:23} some random text {key:name}";
var n = str.replace(/\{key:[\d]+\}/gi, function myFunction(x){return x.replace(/\{key:/,'<span>').replace(/\}/, '</span>');});
this way only {key:AnyNumber} gets replaced, and {key:AnyThingOtherThanNumbers} don't get touched.

It seems you are new to regex. You need to learn more about character classes and capturing groups and backreferences.
The regex is somewhat basic in your case if you do not need any nested encapsulated text support.
Let's start:
The beginning is {key: - it will match the substring literally. Note that { can be a special character (denoting start of a limiting quantifier), thus, it is a good idea to escape it: {key:.
([^}]+) - This is a bit more interesting: the round brackets around are a capturing group that let us later back-reference the matched text. The [^}]+ means 1 or more characters (due to +) other than } (as [^}] is a negated character class where ^ means not)
} matches a } literally.
In the replacement string, we'll get the captured text using a backreference $1.
So, the entire regex will look like:
{key:([^}]+)}
See demo on regex101.com
Code snippet:
var re = /{key:([^}]+)}/g;
var str = '{key:23}';
var subst = '<span class="highlightable">$1</span>';
document.getElementById("res").innerHTML = str.replace(re, subst);
.highlightable
{
color: red;
}
<div id="res"/>
If you want to use a different behavior based on the value of key, then you'll need to adjust the regex to either match digits only (with \d+) or letters only (say, with [a-zA-Z] for English), or other shorthand classes, ranges (= character classes), or their combinations.

If your string is in var a, then:
var test = a.replace( /\{key:(\d+)\}/g, "<span class='highlightable'>$1</span>");

Split string in JavaScript using a regular expression

I'm trying to write a regex for use in javascript.
var script = "function onclick() {loadArea('areaog_og_group_og_consumedservice', '\x26roleOrd\x3d1');}";
var match = new RegExp("'[^']*(\\.[^']*)*'").exec(script);
I would like split to contain two elements:
match[0] == "'areaog_og_group_og_consumedservice'";
match[1] == "'\x26roleOrd\x3d1'";
This regex matches correctly when testing it at gskinner.com/RegExr/ but it does not work in my Javascript. This issue can be replicated by testing ir here http://www.regextester.com/.
I need the solution to work with Internet Explorer 6 and above.
Can any regex guru's help?

Judging by your regex, it looks like you're trying to match a single-quoted string that may contain escaped quotes. The correct form of that regex is:
'[^'\\]*(?:\\.[^'\\]*)*'
(If you don't need to allow for escaped quotes, /'[^']*'/ is all you need.) You also have to set the g flag if you want to get both strings. Here's the regex in its regex-literal form:
/'[^'\\]*(?:\\.[^'\\]*)*'/g
If you use the RegExp constructor instead of a regex literal, you have to double-escape the backslashes: once for the string literal and once for the regex. You also have to pass the flags (g, i, m) as a separate parameter:
var rgx = new RegExp("'[^'\\\\]*(?:\\\\.[^'\\\\]*)*'", "g");
while (result = rgx.exec(script))
print(result[0]);

The regex you're looking for is .*?('[^']*')\s*,\s*('[^']*'). The catch here is that, as usual, match[0] is the entire matched text (this is very normal) so it's not particularly useful to you. match[1] and match[2] are the two matches you're looking for.
var script = "function onclick() {loadArea('areaog_og_group_og_consumedservice', '\x26roleOrd\x3d1');}";
var parameters = /.*?('[^']*')\s*,\s*('[^']*')/.exec(script);
alert("you've done: loadArea("+parameters[1]+", "+parameters[2]+");");
The only issue I have with this is that it's somewhat inflexible. You might want to spend a little time to match function calls with 2 or 3 parameters?
EDIT
In response to you're request, here is the regex to match 1,2,3,...,n parameters. If you notice, I used a non-capturing group (the (?: ) part) to find many instances of the comma followed by the second parameter.
/.*?('[^']*')(?:\s*,\s*('[^']*'))*/

Maybe this:
'([^']*)'\s*,\s*'([^']*)'