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freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/regular-expressions/find-characters-with-lazy-matching.md
Nicholas Carrigan (he/him) 7117919d36 chore(learn): audit javascript algorithms and data structures (#41092)
* chore(learn): audit basic algorithm scripting

* chore(learn): audit basic data structures

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* chore(learn): audit regex

* fix(learn): remove stray .

* fix(learn): string to code

* fix(learn): missed some

* fix(learn): clarify strings

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were removed in favour of back ticks.

* fix: apply suggestions - thanks Randy! :)

Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com>

* fix: non-suggestion comments

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Removes the comments from the description and instruction code
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* fix: Apply suggestions from code review

Co-authored-by: Shaun Hamilton <51722130+ShaunSHamilton@users.noreply.github.com>

* fix: revert crowdin fix

* Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-algorithm-scripting/mutations.md

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* fix: Apply suggestions from code review

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* Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/es6/use-destructuring-assignment-to-assign-variables-from-arrays.md

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* fix: Apply suggestions from code review

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* chore: change voice

* fix: Christopher Nolan

* fix: expressions would evaluate

* fix: will -> would

* Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/object-oriented-programming/add-methods-after-inheritance.md

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* fix: to work to push

* Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/iterate-with-javascript-for-loops.md

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* Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/object-oriented-programming/add-methods-after-inheritance.md

Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com>

Co-authored-by: Randell Dawson <5313213+RandellDawson@users.noreply.github.com>
Co-authored-by: Shaun Hamilton <51722130+ShaunSHamilton@users.noreply.github.com>
Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>
2021-03-02 17:12:12 -07:00

1.8 KiB

id, title, challengeType, forumTopicId, dashedName
id title challengeType forumTopicId dashedName
587d7db6367417b2b2512b9b Find Characters with Lazy Matching 1 301341 find-characters-with-lazy-matching

--description--

In regular expressions, a greedy match finds the longest possible part of a string that fits the regex pattern and returns it as a match. The alternative is called a lazy match, which finds the smallest possible part of the string that satisfies the regex pattern.

You can apply the regex /t[a-z]*i/ to the string "titanic". This regex is basically a pattern that starts with t, ends with i, and has some letters in between.

Regular expressions are by default greedy, so the match would return ["titani"]. It finds the largest sub-string possible to fit the pattern.

However, you can use the ? character to change it to lazy matching. "titanic" matched against the adjusted regex of /t[a-z]*?i/ returns ["ti"].

Note: Parsing HTML with regular expressions should be avoided, but pattern matching an HTML string with regular expressions is completely fine.

--instructions--

Fix the regex /<.*>/ to return the HTML tag <h1> and not the text "<h1>Winter is coming</h1>". Remember the wildcard . in a regular expression matches any character.

--hints--

The result variable should be an array with <h1> in it

assert(result[0] == '<h1>');

myRegex should use lazy matching

assert(/\?/g.test(myRegex));

myRegex should not include the string h1

assert(!myRegex.source.match('h1'));

--seed--

--seed-contents--

let text = "<h1>Winter is coming</h1>";
let myRegex = /<.*>/; // Change this line
let result = text.match(myRegex);

--solutions--

let text = "<h1>Winter is coming</h1>";
let myRegex = /<.*?>/; // Change this line
let result = text.match(myRegex);