javascript, regex parse string content in curly brackets - javascript

i am new to regex. I am trying to parse all contents inside curly brackets in a string. I looked up this post as a reference and did exactly as one of the answers suggest, however the result is unexpected.
Here is what i did
var abc = "test/abcd{string1}test{string2}test" //any string
var regex = /{(.+?)}/
regex.exec(abc) // i got ["{string1}", "string1"]
//where i am expecting ["string1", "string2"]
i think i am missing something, what am i doing wrong?
update
i was able to get it with /g for a global search
var regex = /{(.*?)}/g
abc.match(regex) //gives ["{string1}", "{string2}"]
how can i get the string w/o brackets?

"test/abcd{string1}test{string2}test".match(/[^{}]+(?=\})/g)
produces
["string1", "string2"]
It assumes that every } has a corresponding { before it and {...} sections do not nest. It will also not capture the content of empty {} sections.

var abc = "test/abcd{string1}test{string2}test" //any string
var regex = /{(.+?)}/g
var matches;
while(matches = regex.exec(abc))
console.log(matches);

Try this:
var abc = "test/abcd{string1}test{string2}test" //any string
var regex = /{(.+?)}/g //g flag so the regex is global
abc.match(regex) //find every match
a good place to read about Regex in javascript is here, and a nice place to test is here
good luck!

Nothing wrong. But you'll need to look at your capturing groups (the second element in the array) to get the content you wanted (you can ignore the first). To get all occurences, it's not enough to run exec once, you'll need to loop over the results using match.
Edit: nevermind that, afaik you can't access capturing groups with match. A simpler solution would be using a positive lookahead, as Mike Samuel suggested.

This result:
["{string1}", "string1"]
is showing you that for the first match, the entire regex matched "{string1}" and the first capturing parentheses matched "string1".
If you want to get all matches and see all capturing parens of each match, you can use the "g" flag and loop through, calling exec() multiple times like this:
var abc = "test/abcd{string1}test{string2}test"; //any string
var regex = /{(.+?)}/g;
var match, results = [];
while (match = regex.exec(abc)) {
results.push(match[1]); // save first captured parens sub-match into results array
}
// results == ["string1", "string2"]
You can see it work here: http://jsfiddle.net/jfriend00/sapfm/

try this for file
const fs = require('fs');
fs.readFile('logs.txt', function(err, data) {
if(err) throw err;
const paragraph = "'" + data + "'";
const regex = /\d+\<;>\S+\<;>(\d+)\<;/g;
const found = paragraph.match(regex);
console.log(found);
})

Related

Possible to get 'regex source' from match?

I can get the source of a regex when it's defined separately. For example:
let r1 = new RegExp("el*");
console.log(r1.source);
// el*
Or:
let r2 = /el*/;
console.log(r2.source);
// el*
Is there a way to extract that if the regex isn't defined separately? For example, something along the lines of:
let m = "Hello".match(/el*/);
console.log(m.source?);
No,
quoting the documents of the match() function
Return value
An Array whose contents depend on the presence or absence of the
global (g) flag, or null if no matches are found.
So the return value is an array (you can test it by Array.isArray(m)// true)
However, the returned array has some extra information about the ocurred match (like groups, index and original input) but none of them include the original regex used to get the match
So there is no way to get that information from the match because its not returned by the matching function
The match result by itself cannot lead to the original regex, simply because different regexes can lead to the same result, even on the same string. Take for example the string "abcd" - all the following regexes: /abcd/, /a..d/ /a.*/ and many more, would match the string exactly the same way.
The only way you could retrive the original regex is if a reference to the regex was literally stored by the match() method inside the returned object. There is no reason to think that's the case, but you can implement your own match function that would do. Something like
function myMatch(str, regex) {
var match = str.match(regex);
if (match === null) {
match = [null];
}
match.source = regex;
return match;
}

Regex - Match a string between second occurance of characters

I have a string of text that looks something like this:
?q=search&something=that&this=example/
In that example, I need to grab that . I'm using the following regex below:
var re = new RegExp("\&(.*?)\&");
Which going re[1] is giving me:
something=that - but it needs to be only that
I tried:
var re = new RegExp("\=(.*?)\&");
But that gives me everything from the first equals sign, so:
search&something=that
Is the output when it just needs to be:
that
I need to somehow target the second occurrences of 2 characters and grab whats in between them. How best do I go about this?
You can use
/something=([^&]+)/
and take the first group, see the JavaScript example:
let url = '?q=search&something=that&this=example/';
let regex = /something=([^&]+)/
let match = regex.exec(url);
console.log(match[1]);
split seems more suited to your case:
"?q=search&something=that&this=example/".split("&")[1].split("=")[1]
Then you could also implement a simple method to extract any wanted value :
function getValue(query, index) {
const obj = query.split("&")[index];
if(obj) obj.split("=")[1]
}
getValue("?q=search&something=that&this=example/", 1);

Whats wrong with this regex logic

I am trying to fetch the value after equal sign, its works but i am getting duplicated values , any idea whats wrong here?
// Regex for finding a word after "=" sign
var myregexpNew = /=(\S*)/g;
// Regex for finding a word before "=" sign
var mytype = /(\S*)=/g;
//Setting data from Grid Column
var strNew = "QCById=20";
var matchNew = myregexpNew.exec(strNew);
var newtype = mytype.exec(strNew);
alert(matchNew);
https://jsfiddle.net/6vjjv0hv/
exec returns an array, the first element is the global match, the following ones are the submatches, that's why you get ["=20", "20"] (using console.log here instead of alert would make it clearer what you get).
When looking for submatches and using exec, you're usually interested in the elements starting at index 1.
Regarding the whole parsing, it's obvious there are better solution, like using only one regex with two submatches, but it depends on the real goal.
You can try without using Regex like this:
var val = 'QCById=20';
var myString = val.substr(val.indexOf("=") + 1);
alert(myString);
Presently exec is returning you the matched value.
REGEXP.exec(SOMETHING) returns an array (see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec).
The first item in the array is the full match and the rest matches the parenthesized substrings.
You do not get duplicated values, you just get an array of a matched value and the captured text #1.
See RegExp#exec() help:
If the match succeeds, the exec() method returns an array and updates properties of the regular expression object. The returned array has the matched text as the first item, and then one item for each capturing parenthesis that matched containing the text that was captured.
Just use the [1] index to get the captured text only.
var myregexpNew = /=(\S*)/g;
var strNew = "QCById=20";
var matchNew = myregexpNew.exec(strNew);
if (matchNew) {
console.log(matchNew[1]);
}
To get values on both sides of =, you can use /(\S*)=(\S*)/g regex:
var myregexpNew = /(\S*)=(\S*)/g;
var strNew = "QCById=20";
var matchNew = myregexpNew.exec(strNew);
if (matchNew) {
console.log(matchNew[1]);
console.log(matchNew[2]);
}
Also, you may want to add a check to see if the captured values are not undefined/empty since \S* may capture an empty string. OR use /(\S+)=(\S+)/g regex that requires at least one non-whitespace character to appear before and after the = sign.

Why am I getting a single value from my regex.exec?

I have a very simple code:
var allTypes = "restaurant|dentist";
var typeSplitter = new RegExp("([a-zA-Z]+)");
typeSplitter.exec(allTypes);
I want an array like this:
["restaurant", "dentist"]
But instead I get this:
["restaurant", "restaurant"]
I did test my regex here. I've been fiddling for way to long with this, probably something I don't know about
Just do this
allTypes.split('|');
// => ['restaurant', 'dentist']
.split can also take a regex; even though it's not necessary in this case
allTypes.split(/[|]/);
But if you really want to use regex to capture, you have to use .match
matches = allTypes.match(/([a-zA-Z]+)/g); // g = global modifier
Because exec returns only one match and all captures. The first element is the full match. The second one the first capture (the first set of parentheses in your pattern). Since you have wrapped the entire pattern in parentheses, these values coincide (and your parentheses are unnecessary). Use match and a global modifier instead:
var result = "restaurant|dentist".match(/[a-zA-Z]+/g);
If you have a more complex pattern and you do need the capturing groups for every match, then exec is the way to go. But you still need to use the global modifier and run exec in a loop:
var regex = /your(Pattern)here/g;
var m;
while (m = regex.exec(input))
{
var entireMatch = m[0];
var firstCapture = m[1];
// ...
// process results
}

Javascript Regexp - Match Characters after a certain phrase

I was wondering how to use a regexp to match a phrase that comes after a certain match. Like:
var phrase = "yesthisismyphrase=thisiswhatIwantmatched";
var match = /phrase=.*/;
That will match from the phrase= to the end of the string, but is it possible to get everything after the phrase= without having to modify a string?
You use capture groups (denoted by parenthesis).
When you execute the regex via match or exec function, the return an array consisting of the substrings captured by capture groups. You can then access what got captured via that array. E.g.:
var phrase = "yesthisismyphrase=thisiswhatIwantmatched";
var myRegexp = /phrase=(.*)/;
var match = myRegexp.exec(phrase);
alert(match[1]);
or
var arr = phrase.match(/phrase=(.*)/);
if (arr != null) { // Did it match?
alert(arr[1]);
}
phrase.match(/phrase=(.*)/)[1]
returns
"thisiswhatIwantmatched"
The brackets specify a so-called capture group. Contents of capture groups get put into the resulting array, starting from 1 (0 is the whole match).
It is not so hard, Just assume your context is :
const context = "https://example.com/pa/GIx89GdmkABJEAAA+AAAA";
And we wanna have the pattern after pa/, so use this code:
const pattern = context.match(/pa\/(.*)/)[1];
The first item include pa/, but for the grouping second item is without pa/, you can use each what you want.
Let try this, I hope it work
var p = /\b([\w|\W]+)\1+(\=)([\w|\W]+)\1+\b/;
console.log(p.test('case1 or AA=AA ilkjoi'));
console.log(p.test('case2 or AA=AB'));
console.log(p.test('case3 or 12=14'));
If you want to get value after the regex excluding the test phrase, use this:
/(?:phrase=)(.*)/
the result will be
0: "phrase=thisiswhatIwantmatched" //full match
1: "thisiswhatIwantmatched" //matching group

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