3.1 KiB
3.1 KiB
id, title, challengeType
id | title | challengeType |
---|---|---|
587d7dbb367417b2b2512baa | Reuse Patterns Using Capture Groups | 1 |
Description
capture groups
. Parentheses, (
and )
, are used to find repeat substrings. You put the regex of the pattern that will repeat in between the parentheses.
To specify where that repeat string will appear, you use a backslash (\
) and then a number. This number starts at 1 and increases with each additional capture group you use. An example would be \1
to match the first group.
The example below matches any word that occurs twice separated by a space:
let repeatStr = "regex regex";
let repeatRegex = /(\w+)\s\1/;
repeatRegex.test(repeatStr); // Returns true
repeatStr.match(repeatRegex); // Returns ["regex regex", "regex"]
Using the .match()
method on a string will return an array with the string it matches, along with its capture group.
Instructions
capture groups
in reRegex
to match numbers that are repeated only three times in a string, each separated by a space.
Tests
tests:
- text: Your regex should use the shorthand character class for digits.
testString: assert(reRegex.source.match(/\\d/));
- text: Your regex should reuse a capture group twice.
testString: assert(reRegex.source.match(/\\1|\\2/g).length >= 2);
- text: Your regex should have two spaces separating the three numbers.
testString: assert(reRegex.source.match(/ |\\s/g).length === 2 || reRegex.source.match(/\(\\s\)(?=.*\\(1|2))/g));
- text: Your regex should match <code>"42 42 42"</code>.
testString: assert(reRegex.test("42 42 42"));
- text: Your regex should match <code>"100 100 100"</code>.
testString: assert(reRegex.test("100 100 100"));
- text: Your regex should not match <code>"42 42 42 42"</code>.
testString: assert.equal(("42 42 42 42").match(reRegex.source), null);
- text: Your regex should not match <code>"42 42"</code>.
testString: assert.equal(("42 42").match(reRegex.source), null);
- text: Your regex should not match <code>"101 102 103"</code>.
testString: assert(!reRegex.test("101 102 103"));
- text: Your regex should not match <code>"1 2 3"</code>.
testString: assert(!reRegex.test("1 2 3"));
- text: Your regex should match <code>"10 10 10"</code>.
testString: assert(reRegex.test("10 10 10"));
Challenge Seed
let repeatNum = "42 42 42";
let reRegex = /change/; // Change this line
let result = reRegex.test(repeatNum);
Solution
let repeatNum = "42 42 42";
let reRegex = /^(\d+)\s\1\s\1$/;
let result = reRegex.test(repeatNum);