What will be the regular expression for below requirement in javascript - javascript

Criteria:
any word that start with a and end with b having middle char digit. this word should not be on the line which start with char '#'
Given string:
a1b a2b a3b
#a4b a5b a6b
a7b a8b a9b
Expected output:
a1b
a2b
a3b
a7b
a8b
a9b
regex: ?i need it for javascipt.
So far tried below thing:
var text_content =above_mention_content
var reg_exp = /^[^#]?a[0-9]b/gmi;
var matched_text = text_content.match(reg_exp);
console.log(matched_text);
Getting below output:
[ 'a1b', ' a7b' ]

Your /^[^#]?a[0-9]b/gmi will match multiple occurrences of the pattern matching the start of line, then 1 or 0 chars other than #, then a, digit and b. No checking for a whole word, nor actually matching words farther than at the beginning of a string.
You may use a regex that will match lines starting with # and match and capture the words you need in other contexts:
var s = "a1b a2b a3b\n#a4b a5b a6b\n a7b a8b a9b";
var res = [];
s.replace(/^[^\S\r\n]*#.*|\b(a\db)\b/gm, function($0,$1) {
if ($1) res.push($1);
});
console.log(res);
Pattern details:
^ - start of a line (as m multiline modifier makes ^ match the line start)
[^\S\r\n]* - 0+ horizontal whitespaces
#.* - a # and any 0+ chars up to the end of a line
| - or
\b - a leading word boundary
(a\db) - Group 1 capturing a, a digit, a b
\b - a trailing word boundary.
Inside the replace() method, a callback is used where the res array is populated with the contents of Group 1 only.

I would suggest to use 2 reg ex:
First Reg ex fetches the non-hashed lines:
^[^#][a\db\s]+
and then another reg ex for fetching individual words(from each line):
^a\db\s

Related

Javascript regex to find two characters between two delimitators

EDITED
I need to find two characters between '[' ']' and '/' '/' using Javascript.
I am using this regex:
([^.][/[string]]|\/string\/)|(\[(string))|(\/(string))| ((string)\])|((string)\/)
that gets two charactes but gets too one character.
The question is, how can I do to get just two characters?
Also I want to get exactly the two characters inside the string, I mean not just only the exact match.
Eg.
User input: dz
It must to find just exact matches that contains "dz", e.g. --> "dzone" but not "dazone". Currently I am getting matches with both strings, "dzone" and "dazone".
Demo: https://regex101.com/r/FEs6ib/1
You could optionally repeat any char except the delimiters between the delimiters them selves, and capture in a group what you want to keep.
If you want multiple matches for /dzone/dzone/ you could assert the last delimiter to the right instead of matching it.
The matches are in group 1 or group 2 where you can check for if they exist.
\/[^\/]*(dz)[^\/]*(?=\/)|\[[^\][]*(dz)[^\][]*(?=])
The pattern matches:
\/ Match /
[^\/]*(dz)[^\/]* Capture dz in group 1 between optional chars other than /
(?=\/) Positive lookahead, assert / to the right
| Or
\[ Match [
[^\][]*(dz)[^\][]* Capture dz in group 2 between optional chars other than [ and ]
-(?=]) Positive lookahead, assert ] to the right
Regex demo
This will match 1 occurrence of dz in the word. If you want to match the whole word, the capture group can be broadened to before and after the negated character class like:
\/([^\/]*dz[^\/]*)(?=\/)|\[([^\][]*dz[^\][]*)(?=])
Regex demo
const regex = /\/[^\/]*(dz)[^\/]*(?=\/)|\[[^\][]*(dz)[^\][]*(?=])/g;
[
"[dzone]",
"/dzone/",
"/dzone/dzone/",
"/testdztest/",
"[dazone]",
"/dazone/",
"dzone",
"dazone"
].forEach(s =>
console.log(
`${s} --> ${Array.from(s.matchAll(regex), m => m[2] ? m[2] : m[1])}`
)
);
If supported, you might also match all occurrences of dz between the delimiters using lookarounds with an infinite quantifier:
(?<=\/[^\/]*)dz(?=[^\/]*\/)|(?<=\[[^\][]*)dz(?=[^\][]*])
Regex demo
const regex = /(?<=\/[^\/]*)dz(?=[^\/]*\/)|(?<=\[[^\][]*)dz(?=[^\][]*])/g;
[
"[adzadzone]",
"[dzone]",
"/dzone/",
"/dzone/dzone/",
"/testdztest/",
"[dazone]",
"/dazone/",
"dzone",
"dazone"
].forEach(s => {
const m = s.match(regex);
if (m) {
console.log(`${s} --> ${s.match(regex)}`);
}
});

Regex to match many times

I'm trying to match a type definition
def euro : t1 -> t2 -> t3 (and this pattern my repeat further in other examples)
I came up with this regex
^def ([^\s]*)\s:\s([^\s]*)(\s->\s[^\s]*)*
But while it matches euro and t1 it
then matches -> t2 rather than t2
fails to match anything with t3
I can't see what I am doing wrong, and my goal is to capture
euro t1 t2 t3
as four separate items, and what I currently get is
0: "def euro : t1 -> t2 -> t3"
1: "euro"
2: "t1"
3: " -> t3"
You can't use a repeated capturing group in JS regex, all but the last values will be "dropped", re-written upon each subsequent iteration.
When creating a regular expression that needs a capturing group to grab part of the text matched, a common mistake is to repeat the capturing group instead of capturing a repeated group. The difference is that the repeated capturing group will capture only the last iteration, while a group capturing another group that's repeated will capture all iterations.
The way out can be capturing the whole substring and then split it. Here is an example:
var s = "def euro : t1 -> t2 -> t3";
var rx = /^def (\S*)\s:\s(\S*)((?:\s->\s\S*)*)/;
var res = [];
var m = s.match(rx);
if (m) {
res = [m[1], m[2]];
for (var s of m[3].split(" -> ").filter(Boolean)) {
res.push(s);
}
}
console.log(res);
Pattern details
^ - start of string
def - a literal substring
(\S*) - Capturing group 1: 0+ non-whitespace chars
\s:\s - a : enclosed with single whitespaces
(\S*) - Capturing group 2: 0+ non-whitespace chars
((?:\s->\s\S*)*) - Capturing group 3: 0+ repetitions of the following pattern sequences:
\s->\s - whitespace, ->, whitespace
\S* - 0+ non-whitespace chars
Details:
?: - creates a non-capturing group
$1 - recieves the result of first capturing group i.e., \w+
\s[\:\-\>]+\s - matches " : " or " -> "
\w+ - matches repeating alphanumeric pattern
let str = 'def euro : t1 -> t2 -> t3';
let regex = /(?:def\s|\s[\:\-\>]+\s)(\w+)/g;
let match = str.replace(regex, '$1\n').trim().split('\n');
console.log(match);

Filter version number from string in javascript?

I found some threads about extracting version number from a string on here but none that does exactly what I want.
How can I filter out the following version numbers from a string with javascript/regex?
Title_v1_1.00.mov filters 1
v.1.0.1-Title.mp3 filters 1.0.1
Title V.3.4A. filters 3.4A
V3.0.4b mix v2 filters 3.0.4b
So look for the first occurrence of: "v" or "v." followed by a digit, followed by digits, letters or dots until either the end of the string or until a whitepace occurs or until a dot (.) occurs with no digit after it.
As per the comments, to match the first version number in the string you could use a capturing group:
^.*?v\.?(\d+(?:\.\d+[a-z]?)*)
Regex demo
That will match:
^ Assert the start of the string
.*? Match 0+ any character non greedy
v\.? Match v followed by an optional dot
( Capturing group
\d+ Match 1+ digits
(?: Non capturing group
\.\d+[a-z]? Match a dot, 1+ digits followed by an optional character a-z
)* Close non capturing group and repeat 0+ times
) Close capturing group
If the character like A in V.3.4A can only be in the last part, you could use:
^.*?v\.?(\d+(?:\.\d+)*[a-z]?)
const strings = [
"Title_v1_1.00.mov filters 1",
"v.1.0.1-Title.mp3 filters 1.0.1",
"Title V.3.4A. filters 3.4A",
"V3.0.4b mix v2 filters 3.0.4b"
];
let pattern = /^.*?v\.?(\d+(?:\.\d+[a-z]?)*)/i;
strings.forEach((s) => {
console.log(s.match(pattern)[1]);
});
Details:
v - character "v"
(?:\.)? - matches 1 or 0 repetition of "."
Version capturing group
[0-9a-z\.]* - Matches alphanumeric and "." character
[0-9a-z] - ensures that version number don't ends with "."
You can use RegExp.exec() method to extract matches from string one by one.
const regex = /v(?:\.?)([0-9a-z\.]*[0-9a-z]).*/gi;
let str = [
"Title_v1_1.00.mov filters 1",
"v.1.0.1-Title.mp3 filters 1.0.1",
"Title V.3.4A. filters 3.4A",
"V3.0.4b mix v2 filters 3.0.4b"
];
let versions = [];
let v; // variable to store match
for(let i = 0; i < str.length; i++) {
// Executes a check on str[i] to get the result of first capturing group i.e., our version number
if( (v = regex.exec(str[i])) !== null)
versions.push(v[1]); // appends the version number to the array
// If not found, then it checks again if there is a match present or not
else if(str[i].match(regex) !== null)
i--; // if match found then it loops over the same string again
}
console.log(versions);
var test = [
"Title_v1_1.00.mov filters 1",
"v.1.0.1-Title.mp3 filters 1.0.1",
"Title V.3.4A. filters 3.4A",
"V3.0.4b mix v2 filters 3.0.4b",
];
console.log(test.map(function (a) {
return a.match(/v\.?([0-9a-z]+(?:\.[0-9a-z]+)*)/i)[1];
}));
Explanation:
/ # regex delimiter
v # letter v
\.? # optional dot
( # start group 1, it will contain the version number
[0-9a-z]+ # 1 or more alphanumeric
(?: # start non capture group
\. # a dot
[0-9a-z]+ # 1 or more alphanumeric
)* # end group, may appear 0 or more times
) # end group 1
/i # regex delimiter and flag case insensitive

Javascript: Replace needle in haystack that is not between two characters

I'd like to replace a needle in a haystack that is not between two characters.
So say I have a regular expression that is /\bneedle\b/g, that will match all needle's that are not next to any word character. I want to expand on this and include needle's that are not next to any word character, and NOT between two characters such as [ and ]
So the first three needles will match but the rest will not: needle: needle's needle [needle] [needle something] needle1 needler
Any idea how I'd go about doing this?
You can use this regex:
/(^|[^\w\[])(needle)(?![\w\]])/
RegEx Demo
Breakup:
(^|[^\w\[]) # line start OR a non-word non-[ character
(needle) # match and group our targeted text
(?![\w\]]) # negative lookahead to fail the match if next char is word char or [
As per comments below you can use following replace code:
var str = "needle: needle's needle [needle] [needle something] needle1 needler";
var reg = new RegExp("(^|[^\\w\\[])(needle)(?![\\w\\]])", "gi");
str = str.replace(reg, "$1*$2*");
//=> *needle*: *needle*'s *needle* [needle] [needle something] needle1 needler

RegExp match word till space or character

I'm trying to match all the words starting with # and words between 2 # (see example)
var str = "#The test# rain in #SPAIN stays mainly in the #plain";
var res = str.match(/(#)[^\s]+/gi);
The result will be ["#The", "#SPAIN", "#plain"] but it should be ["#The test#", "#SPAIN", "#plain"]
Extra: would be nice if the result would be without the #.
Does anyone has a solution for this?
You can use
/#\w+(?:(?: +\w+)*#)?/g
See the demo here
The regex matches:
# - a hash symbol
\w+ - one or more alphanumeric and underscore characters
(?:(?: +\w+)*#)? - one or zero occurrence of:
(?: +\w+)* - zero or more occurrences of one or more spaces followed with one or more word characters followed with
# - a hash symbol
NOTE: If there can be characters other than word characters (those in the [A-Za-z0-9_] range), you can replace \w with [^ #]:
/#[^ #]+(?:(?: +[^ #]+)*#)?/g
See another demo
var re = /#[^ #]+(?:(?: +[^ #]+)*#)?/g;
var str = '#The test-mode# rain in #SPAIN stays mainly in the #plain #SPAIN has #the test# and more #here';
var m = str.match(re);
if (m) {
// Using ES6 Arrow functions
m = m.map(s => s.replace(/#$/g, ''));
// ES5 Equivalent
/*m = m.map(function(s) {
return s.replace(/#$/g, '');
});*/ // getting rid of the trailing #
document.body.innerHTML = "<pre>" + JSON.stringify(m, 0, 4) + "</pre>";
}
You can also try this regex.
#(?:\b[\s\S]*?\b#|\w+)
(?: opens a non capture group for alternation
\b matches a word boundary
\w matches a word character
[\s\S] matches any character
See demo at regex101 (use with g global flag)

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