I have text of a form where there are paragraphs of text with urls interspersed.
I would like to parse the string creating html links from the urls and using the following text as the descriptive link text i.e.
possibly some text here http://www.somewebsite.com/some/path/somepage.html descriptive text which may or may not be present
into
descriptive text which may or may not be present
This SO article, JS: Find URLs in Text, Make Links, is relevant to what I'm attempting to do but simply places the url as the text within the anchor element.
I am successfully matching the url with
var urlRE= new RegExp("([a-zA-Z0-9]+://)?([a-zA-Z0-9_]+:[a-zA-Z0-9_]+#)?([a-zA-Z0-9.-]+\\.[A-Za-z]{2,4})(:[0-9]+)?([^ ])+");
but am unsure how to perform the match afterwards.
I came across this post Regex - Matching text AFTER certain characters which seems applicable. I've attempted to wrap my RE in /(?<=my url pattern here).+/ but get an error stating that there is an invalid group and that this results in an invalid RE.
In that post J-Law mentions that
Variable-length lookbehinds aren’t allowed
Is this what I'm attempting to do?
Since I'm already matching the url I feel like I could easily do some substring math to get the desired results.
I'm just using this as an attempt to learn more about regex.
Thanks
Just add another capturing group to capture all the stuff at the end and make your inner groups non-capturing. Something like:
var urlRE= new RegExp("((?:[a-zA-Z0-9]+://)?(?:[a-zA-Z0-9_]+:[a-zA-Z0-9_]+#)?(?:[a-zA-Z0-9.-]+\\.[A-Za-z]{2,4})(?::[0-9]+)?(?:[^ ])+)(.*)$");
var s = "possibly some text here http://www.somewebsite.com/some/path/somepage.html descriptive text which may or may not be present"
var match = urlRE.exec(s);
alert(match[0] + "\n\n" + match[1] + "\n\n" + match[2]);
// Returns:
// ["http://www.somewebsite.com/some/path/somepage.html descriptive text which may or may not be present",
// "http://www.somewebsite.com/some/path/somepage.html",
// " descriptive text which may or may not be present"]
I wrapped your entire regex in brackets () to form the first capturing group and inside that I made all your existing groups non-capturing with ?:, You don't absolutely need to do that (making them non-capturing), but it does simplify the output. Then I just added one more group (.*) to capture everything else until the end of the string $.
After .exec if you have a match, your match will be in [0], the url part will be in [1] and the rest of your text in [2]. This is why we used the non-capturing groups because otherwise you'd have a bunch of other captures that may or may not be useful.
Related
I am trying to do some html scraping with JavaScript, and would like to take the a href link and replace it into a hyperlink on a Discord embed. I am having trouble with regex, I am finding it very difficult to learn.
I assume I will also need another regex to capture it all so I can replace it with my desired target?
This is an example raw html that I have:
An **example**, also known as a example type
to make this readable within a Discord embed, I am looking for a desired output of:
An **example**, also known as a [**example type**](https://www.example.com/example%20type)
I have tried extracting the URL via regex, which I can match however, I am having issues with extracting the link and the (I think its called target? The 'example type' in the example link text) and then replacing the string with my desired output.
I have the following: (https://regexr.com/73574)
/href="[^"]+/g
This matches href="https://www.example.com/example%20type, and feels like a very early step, it includes 'href' in the match, and it does not capture the target.
EDIT:
I apologise, I did not think about additional checks, what if the string has multiple links? and text after them, for example:
An **example**, also known as a example type is the first example, and now I have second example
with a desired output of:
An **example**, also known as a [**example type**](https://www.example.com/example%20type) is the first example, and now I have [**second**](https://www.example.com/second) example
Try this: (?<=href=")[^"]*
By using a lookbehind, you can now verify that the text behind is equal to href=" without capturing it
Demo: https://regex101.com/r/2qMnPt/1
You can use regular expression groups to capture things that interest you. My regular expression here might be far from perfect but I don't think that's important here - it shows you a way and you can always improve it if needed.
Things you have to do:
prepare regex that captures groups that you need (anchor tag, anchor text, anchor url),
remove the anchor tag completely from the text
inject anchor text and anchor href into the final string
Here's a quick code example of that:
const anchorRegex = /(<a\shref="([^"]+)">(.+?)<\/a>)/i;
const textToBeParsed = `An **example**, also known as a example type`;
const parseText = (text) => {
const matches = anchorRegex.exec(textToBeParsed);
if (!matches) {
console.warn("Something went wrong...");
return;
}
const [, fullAnchorTag, anchorUrl, anchorText] = matches;
const textWithoutAnchorTag = text.replace(fullAnchorTag, '');
return `${textWithoutAnchorTag}[**${anchorText}**](${anchorUrl})`;
};
console.log(parseText(textToBeParsed));
Solution:
const input = 'An **example**, also known as a example type first and second here no u and then done noice';
const output = input.replace(/<a href="([^"]+)">([^<]+)<\/a>/g, '[**$2**]($1)')
console.log(output);
Regex breakdown:
<a href=" - Matches the opening <a href" HTML tag
([^"]+) - This is a capturing group, matches a number of characters that are not double quotes
"> - Matches the closing double quotes, including the closing tag '>'
([^<]+) - Another capturing group, matches a number of characters that are not a less than symbol
<\/a> - Matches the closing HTML tag
I then use the replace method seen in my output variable.
Within the replace, you see two options (regex, replaceWith)
The first option is obvious, its the regex. The second option [**$2**]($1), uses the capturing groups we see in the regex, the first group $1 provides the link within the HTML tag, and $2 provides the HTML target (the name after the link, for example in my input variable, the first target you see is: 'example type'.
The only important bits in this option is: $2 and $1, however I wanted to display them in a certain way, [**target**](link).
I'm trying to make a regular expression that finds the tagnames and attributes of elements. For example, if I have this:
<div id="anId" class="aClass">
I want to be able to get an array that looks like this:
["(full match)", "div", "id", "anId", "class", "aClass"]
Currently, I have the regex /<(\S*?)(?: ?(.*?)="(.*?)")*>/, but for some reason it skips over every attribute except for the last one.
var str = '<div id="anId" class="aClass">'
console.log(str.match(/<(\S*)(?: ?(.*?)="(.*?)")*>/));
Regex101: https://regex101.com/r/G0ncwF/2
Another odd thing: if I remove the * after the non-capture group, the capture group in quotes seems to somehow "forget" that it's lazy. (Regex101: https://regex101.com/r/C0UwI8/2)
Why does this happen, and how can I avoid it? I couldn't find any questions/answers that helped me (Python re.finditer match.groups() does not contain all groups from match looked promising, but didn't seem help me at all)
(note: I know there are better ways to get the attributes, I'm just experimenting with regex)
UPDATE:
I've figured out at least why the quantifiers seem to "forget" that they're lazy. It's actually just that the regex is trying to match all the way to the angle brackets. I suppose I must have been thinking that the non-capturing group was "insulating" everything and preventing that from happening, and I didn't see it was still lazy because there was only one angle bracket for it to find.
var str = '"foo" "bar"> "baz>"'
console.log("/\".*?\"/ produces ", str.match(/".*?"/), ", finds first quote, finds text, lazily stops at second quote");
console.log("/\".*?\">/ produces ", str.match(/".*?">/), ", finds first quote, finds text, sees second quote but doesn't see angle bracket, keeps going until it sees \">, lazily stops");
So at least that's solved. But I still don't understand why it skips over every attribute but the last one.
And note: Other regexes using different tricks to find the attributes are nice and all, but I'm mostly looking to learn why my regex skips over the attributes, so I can maybe understand regex a bit better.
Playing along with your experimentation you could do this: Instead of scanning for what you want, you can scan for what you don't want, and then filter it out:
const html = '<div id="anId" class="aClass">';
const regex = /[<> ="]/;
let result = html.split(regex).filter(Boolean);
console.log('result: '+JSON.stringify(result));
Output:
result: ["div","id","anId","class","aClass"]
Explanation:
regex /[<> ="]/ lists all chars you don't want
.split(regex) splits your text along the unwanted chars
.filter(Boolean) gets rid of the unwanted chars
Mind you this has flaws, for example it will split incorrectly for html <div id="anId" class="aClass anotherClass">, e.g a space in an attribute value. To support that you could preprocess the html with another regex to escape spaces in quotes, then postprocess with another regex to restore the spaces...
Yes, an HTML parser is more reliable for these kind of tasks.
I have the following string that will occur repeatedly in a larger string:
[SM_g]word[SM_h].[SM_l] "
Notice in this string after the phrase "[SM_g]word[Sm_h]" there are three components:
A period (.) This could also be a comma (,)
[SM_l]
"
Zero to all three of these components will always appear after "[SM_g]word[SM_h]". However, they can also appear in any order after "[SM_g]word[SM_h]". For example, the string could also be:
[SM_g]word[SM_h][SM_l]"
or
[SM_g]word[SM_h]"[SM_l].
or
[SM_g]word[SM_h]".
or
[SM_g]word[SM_h][SM_1].
or
[SM_g]word[SM_h].
or simply just
[SM_g]word[SM_h]
These are just some of the examples. The point is that there are three different components (more if you consider the period can also be a comma) that can appear after "[SM_h]word[SM_g]" where these three components can be in any order and sometimes one, two, or all three of the components will be missing.
Not only that, sometimes there will be up to one space before " and the previous component/[SM_g]word[SM_h].
For example:
[SM_g]word[SM_h] ".
or
[SM_g]word[SM_h][SM_l] ".
etc. etc.
I am trying to process this string by moving each of the three components inside of the core string (and preserving the space, in case there is a space before &\quot; and the previous component/[SM_g]word[SM_h]).
For example, [SM_g]word[SM_h].[SM_l]" would turn into
[SM_g]word.[SM_l]"[SM_h]
or
[SM_g]word[SM_h]"[SM_l]. would turn into
[SM_g]word"[SM_l].[SM_h]
or, to simulate having a space before "
[SM_g]word[SM_h] ".
would turn into
[SM_g]word ".[SM_h]
and so on.
I've tried several combinations of regex expressions, and none of them have worked.
Does anyone have advice?
You need to put each component within an alternation in a grouping construct with maximum match try of 3 if it is necessary:
\[SM_g]word(\[SM_h])((?:\.|\[SM_l]| ?"){0,3})
You may replace word with .*? if it is not a constant or specific keyword.
Then in replacement string you should do:
$1$3$2
var re = /(\[SM_g]word)(\[SM_h])((?:\.|\[SM_l]| ?"){0,3})/g;
var str = `[SM_g]word[SM_h][SM_l] ".`;
console.log(str.replace(re, `$1$3$2`));
This seems applicable for your process, in other word, changing sub-string position.
(\[SM_g])([^[]*)(\[SM_h])((?=([,\.])|(\[SM_l])|( ?&\\?quot;)).*)?
Demo,,, in which all sub-strings are captured to each capture group respectively for your post processing.
[SM_g] is captured to group1, word to group2, [SM_h] to group3, and string of all trailing part is to group4, [,\.] to group5, [SM_l] to group6, " ?&\\?quot;" to group7.
Thus, group1~3 are core part, group4 is trailing part for checking if trailing part exists, and group5~7 are sub-parts of group4 for your post processing.
Therefore, you can get easily matched string's position changed output string in the order of what you want by replacing with captured groups like follows.
\1\2\7\3 or $1$2$7$3 etc..
For replacing in Javascript, please refer to this post. JS Regex, how to replace the captured groups only?
But above regex is not sufficiently precise because it may allow any repeatitions of the sub-part of the trailing string, for example, \1\2\3\5\5\5\5 or \1\2\3\6\7\7\7\7\5\5\5, etc..
To avoid this situation, it needs to adopt condition which accepts only the possible combinations of the sub-parts of the trailing string. Please refer to this example. https://regex101.com/r/6aM4Pv/1/ for the possible combinations in the order.
But if the regex adopts the condition of allowing only possible combinations, the regex will be more complicated so I leave the above simplified regex to help you understand about it. Thank you:-)
I can't post the exact data i'm trying to extract but here's a basic scenario with the same outcome. I'm grabbing the body of a page and trying to extract a bit.ly link from it. So let's say for example, this is the chunk of data where i'm trying to grab the link from.
String:
http://bit.ly/Pq8AkS</div><div class="shareUnit"><div class="-cx-PRIVATE-fbTimelineExternalShareUnit__wrapper"><div><div class="-cx-PRIVATE-fbTimelineExternalShareUnit__root -cx-PRIVATE-fbTimelineExternalShareUnit__hasImage"><a class="-cx-PRIVATE-fbTimelineExternalShareUnit__video -cx-PRIVATE-fbTimelineExternalShareUnit__image -cx-PRIVATE-fbTimelineExternalShareUnit__content" ajaxify="/ajax/flash/expand_inline.php?target_div=uikk85_59&share_id=271663136271285&max_width=403&max_height=403&context=timelineSingle" rel="async" href="#" onclick="CSS.addClass(this, "-cx-PRIVATE-fbTimelineExternalShareUnit__loading");CSS.removeClass(this, "-cx-PRIVATE-fbTimelineExternalShareUnit__video");"><i class="-cx-PRIVATE-fbTimelineExternalShareUnit__play"></i><img class="img" src="http://external.ak.fbcdn.net/safe_image.php?d=AQDoyY7_wjAyUtX2&w=155&h=114&url=http%3A%2F%2Fi1.ytimg.com%2Fvi%2FDre21lBu2zU%2Fmqdefault.jpg" alt="" /></a>
Now, I can get what i'm looking for with the following code but the link isn't always going to be exactly 6 characters long. So this causes an issue...
Body = document.getElementsByTagName("body")[0].innerHTML;
regex = /2Fbit.ly%2F(.{6})&h/g;
Matches = regex.exec(Body);
Here's what I was orginally trying but the problem I have is that it grabs too much data. It's going all the way to the last "&h" in the string above instead of stopping at the first one it hits.
Body = document.getElementsByTagName("body")[0].innerHTML;
regex = /2Fbit.ly%2F(.*)&h/g;
Matches = regex.exec(Body);
So basically the main part of the string i'm trying to focus on is "%2Fbit.ly%2FPq8AkS&h" so that I can get the "Pq8AkS" out of it. When I use the (.*) it's grabbing everything between "%2F" and the very last "&h" in the large string above.
You should not be using a regex on HTML. Use DOM functions to get the desired link object, then get the href attribute from that, then you can use a regex on just the href.
By default .* is greedy meaning that it matches the most it can match and still find a match. If you want it to be non-greedy (match the least possible), you can use this .*? instead like this:
regex = /2Fbit.ly%2F(.*?)&h/;
I also don't think you want the g flag on the regex as there should only be one match in the right URL.
If you show the rest of your HTML, we could offer advice on finding the right link object rather than trying to match the entire body HTML.
FYI, another trick for a non-greedy match is to do something like this:
regex = /2Fbit.ly%2F([^&]*)&h/;
Which matches a series of characters that are not & followed by &h which accomplishes the same goal as long as & can't be in the matched sequence.
By default + and * are greedy and match as much as possible. You need a non-greedy match for your (.+). A quick search gives the solution as
? directly following a quantifier makes the quantifier non-greedy (makes it match minimum instead of maximum of the interval defined).
So try changing your regex= line to
regex = /2Fbit.ly%2F(.*?)&h/g;
Edit: #jfriend00's answer below is more complete.
we have a text like:
this is a test :rep more text more more :rep2 another text text qweqweqwe.
or
this is a test :rep:rep2 more text more more :rep2:rep another text text qweqweqwe. (without space)
we should replace :rep with TEXT1 and :rep2 with TEXT2.
problem:
when try to replace using something like:
rgobj = new RegExp(":rep","gi");
txt = txt.replace(rgobj,"TEXT1");
rgobj = new RegExp(":rep2","gi");
txt = txt.replace(rgobj,"TEXT2");
we get TEXT1 in both of them because :rep2 is similar with :rep and :rep proccess sooner.
If you require that :rep always end with a word boundary, make it explicit in the regex:
new RegExp(":rep\\b","gi");
(If you don't require a word boundary, you can't distinguish what is meant by "hello I got :rep24 eggs" -- is that :rep, :rep2, or :rep24?)
EDIT:
Based on the new information that the match strings are provided by the user, the best solution is to sort the match strings by length and perform the replacements in that order. That way the longest strings get replaced first, eliminating the risk that the beginning of a long string will be partially replaced by a shorter substring match included in that long string. Thus, :replongeststr is replaced before :replong which is replaced before :rep .
If your data is always consistent, replace :rep2 before :rep.
Otherwise, you could search for :rep\s, searching for the space after the keyword. Just make sure you replace the space as well.