I am having having some trouble with a filter function that does not want to do what I need it to do.
I need this array to be filtered for strings within it that contain consecutive repeats of the same letter.
This is what I have:
var regex = /(.)\1+/g;
var filtered = permutations.filter(function(string){
return !string.match(regex);
});
Where permutations is equal to
["a,a,b", "a,a,b", "b,a,a", "a,b,a", "a,b,a", "b,a,a"]
The output for this just shows the same:
["a,a,b", "a,a,b", "b,a,a", "a,b,a", "a,b,a", "b,a,a"]
The output should be:
["a,b,a","a,b,a"]
Any idea what I am doing wrong?
It seems you need to match a repeated char after a comma, thus, change your pattern to
/(.),\1/
See the regex demo
Details:
(.) - Capturing group matching a single char other than a line break char
, - a comma
\1 - backreference to capture group 1.
var regex = /(.),\1/;
var permutations = ["a,a,b", "a,a,b", "b,a,a", "a,b,a", "a,b,a", "b,a,a"];
var filtered = permutations.filter(function(string){
return !regex.test(string);
});
console.log(filtered);
Related
I'm trying to write a regex function that return all of the digits in a comma separated string:
function printDigits() {
var result = sentence.replace(/[^0-9]/g, '').split(",")
console.log(result)
}
But it just prints out a string instead of digits being separated by comma. Are there any ways I can fix this?
Input: "5om3 wr173 w0rd5 u51n9 numb3r5."
Expected output: "5,3,1,7,3,0,5,5,1,9,3,5"
split doesn't work this way. It splits by the separator that is already in the input. To split string to individual characters use split(''), and then join individual characters with comma:
var result = sentence.replace(/[^0-9]/g, '').split('').join(',');
You can use
sentence.match(/\d/g).join(",")
Here,
sentence.match(/\d/g) - extracts each separate digit from string
.join(",") - join the array items into a single comma-delimited string.
See the JavaScript demo:
var sentence = "5om3 wr173 w0rd5 u51n9 numb3r5.";
console.log(sentence.match(/\d/g).join(","));
// -> 5,3,1,7,3,0,5,5,1,9,3,5
Here's another variation that uses pure regex and does not require a .join() call:
sentence.replace(/\D+|(\d)(?=\d)/g, '$1,');
This replaces any string of non-digit characters with a comma. And it also locates the position between two digits and adds a comma between them.
Pattern breakdown:
\D+ - Match one or more non-digit characters.
| - OR...
(\d) - Match one digit and capture it in group 1.
(?=\d) - Followed by another digit.
Substition:
$1, - Replace with whatever was captured in group 1, plus a comma.
Here's a full demo:
var sentence = "5om3 wr173 w0rd5 u51n9 numb3r5";
var result = sentence.replace(/\D+|(\d)(?=\d)/g, '$1,');
console.log(result); // 5,3,1,7,3,0,5,5,1,9,3,5
A reducer solution
const x = `5om3 wr173 w0rd5 u51n9 numb3r5`
.split('')
.reduce((acc, val) =>
val.trim().length && !isNaN(+val) ? [...acc, +val] : acc, []);
console.log(`${x}`);
Or simply
console.log(`${`5om3 wr173 w0rd5 u51n9 numb3r5`.match(/\d/g)}`);
Example data expected output
sds-rwewr-dddd-cash0-bbb cash0
rrse-cash1-nonre cash1
loan-snk-cash2-ssdd cash2
garb-cash3-dfgfd cash3
loan-unwan-cash4-something cash4
The common pattern is here, need to extract a few chars before the last hyphen of given string.
var regex1= /.*(?=(?:-[^-]*){1}$)/g ; //output will be "ds-rwewr-dddd-cash0" from "sds-rwewr-dddd-cash0-bbb "
var regex2 = /\w[^-]*$/g ; //output will be "cash0" from "ds-rwewr-dddd-cash0"
var res =regex2.exec(regex1.exec(sds-rwewr-dddd-cash0-bbb)) //output will cash0
Although above nested regex is working as expected but may not be optimize one. So any help will be appreciated for optimized regex
You can use
/\w+(?=-[^-]*$)/
If the part before the last hyphen can contain chars other than word chars, keep using \w[^-]*: /\w[^-]*(?=-[^-]*$)/. If you do not need to check the first char of your match, simply use /[^-]+(?=-[^-]*$)/.
See the regex demo.
Details:
\w+ - one or more word chars
(?=-[^-]*$) - that must be followed with - and then zero or more chars other than - till the end of string.
JavaScript demo
const texts = ['sds-rwewr-dddd-cash0-bbb','rrse-cash1-nonre','loan-snk-cash2-ssdd','garb-cash3-dfgfd','loan-unwan-cash4-something'];
const regex = /\w+(?=-[^-]*$)/;
for (var text of texts) {
console.log(text, '=>', text.match(regex)?.[0]);
}
string = '1,23'
When a comma is present in the string, I want the regex to match the first digit (\n) after the comma e.g.2.
Sometimes the comma will not be there. When it's not present, I want the regex to match the first digit of the string e.g. 1.
Also, we can't reverse the order of the string to solve this task.
I am genuinely stuck. The only idea I had was prepending this: [,|nothing]. I tried '' to mean nothing but that didn't work.
You can match an optional sequence of chars other than a comma and then a comma at the start of a string, and then match and capture the digit with
/^(?:[^,]*,)?(\d)/
See the regex demo.
Details
^ - start of string
(?:[^,]*,)? - an optional sequence of
[^,]* - 0 any chars other than a comma
, - a comma
(\d) - Capturing group 1: any digit
See the JavaScript demo:
const strs = ['123', '1,23'];
const rx = /^(?:[^,]*,)?(\d)/;
for (const s of strs) {
const result = (s.match(rx) || ['',''])[1];
// Or, const result = s.match(rx)?.[1] || "";
console.log(s, '=>', result);
}
I need to parse a string that comes like this:
-38419-indices-foo-7119-attributes-10073-bar
Where there are numbers followed by one or more words all joined by dashes. I need to get this:
[
0 => '38419-indices-foo',
1 => '7119-attributes',
2 => '10073-bar',
]
I had thought of attempting to replace only the dash before a number with a : and then using .split(':') - how would I do this? I don't want to replace the other dashes.
Imo, the pattern is straight-forward:
\d+\D+
To even get rid of the trailing -, you could go for
(\d+\D+)(?:-|$)
Or
\d+(?:(?!-\d|$).)+
You can see it here:
var myString = "-38419-indices-foo-7119-attributes-10073-bar";
var myRegexp = /(\d+\D+)(?:-|$)/g;
var result = [];
match = myRegexp.exec(myString);
while (match != null) {
// matched text: match[0]
// match start: match.index
// capturing group n: match[n]
result.push(match[1]);
match = myRegexp.exec(myString);
}
console.log(result);
// alternative 2
let alternative_results = myString.match(/\d+(?:(?!-\d|$).)+/g);
console.log(alternative_results);
Or a demo on regex101.com.
Logic
lazy matching using quantifier .*?
Regex
.*?((\d+)\D*)(?!-)
https://regex101.com/r/WeTzF0/1
Test string
-38419-indices-foo-7119-attributes-10073-bar-333333-dfdfdfdf-dfdfdfdf-dfdfdfdfdfdf-123232323-dfsdfsfsdfdf
Matches
Further steps
You need to split from the matches and insert into your desired array.
I have these two strings: "1-2" and "1--2".
I would like to have a regex that would match only the first occurrence of the hyphen in both strings, such that the split would then be: [1,2] and [1,-2]. How would I achieve this, since I have been wracking my brain for too long on this now?
EDIT: The two strings can also occur in the same string such that: "1-2-1--2". Therefore a single regular expression covering both cases would be in order.
You can use this split with a word boundary before -:
let s='1-2-1--2'
let arr = s.split(/\b-/)
console.log(arr)
//=> [1, 2, 1, -2)
You can use simple split(), but with replacement. For example,
var str = '1-2-1--2';
var numArr = str.replace(/--/g, '-~') // The tilde (~) have no mean, this is a charceter for mark a negative number
.split('-')
.map(function(n) { return Number(n.replace('~', '-')); });
console.log(numArr);
I think you're looking for something like this:
(-?[0-9]+)-(-?[0-9]+)
where the first and the second group could have a negative sign
UPDATE:
based on your edit, this implementation would do the job:
var str = '-1--2-2--34-1';
var regex = /(-?\d+)-?/g;
var matches = [];
while((match = regex.exec(str))) {
matches.push(match[1]);
}
console.log(matches);
I prefer using split, but it's fine if you only want to use RegEx.