87 lines
2.3 KiB
Markdown
87 lines
2.3 KiB
Markdown
---
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id: 587d7dbb367417b2b2512bab
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title: Use Capture Groups to Search and Replace
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challengeType: 1
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forumTopicId: 301368
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dashedName: use-capture-groups-to-search-and-replace
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---
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# --description--
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Searching is useful. However, you can make searching even more powerful when it also changes (or replaces) the text you match.
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You can search and replace text in a string using `.replace()` on a string. The inputs for `.replace()` is first the regex pattern you want to search for. The second parameter is the string to replace the match or a function to do something.
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```js
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let wrongText = "The sky is silver.";
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let silverRegex = /silver/;
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wrongText.replace(silverRegex, "blue");
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// Returns "The sky is blue."
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```
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You can also access capture groups in the replacement string with dollar signs (`$`).
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```js
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"Code Camp".replace(/(\w+)\s(\w+)/, '$2 $1');
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// Returns "Camp Code"
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```
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# --instructions--
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Write a regex `fixRegex` using three capture groups that will search for each word in the string "one two three". Then update the `replaceText` variable to replace "one two three" with the string "three two one" and assign the result to the `result` variable. Make sure you are utilizing capture groups in the replacement string using the dollar sign (`$`) syntax.
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# --hints--
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You should use `.replace()` to search and replace.
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```js
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assert(code.match(/\.replace\(.*\)/));
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```
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Your regex should change `"one two three"` to `"three two one"`
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```js
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assert(result === 'three two one');
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```
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You should not change the last line.
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```js
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assert(code.match(/result\s*=\s*str\.replace\(.*?\)/));
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```
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`fixRegex` should use at least three capture groups.
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```js
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assert(new RegExp(fixRegex.source + '|').exec('').length - 1 >= 3);
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```
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`replaceText` should use parenthesized submatch string(s) (i.e. the nth parenthesized submatch string, $n, corresponds to the nth capture group).
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```js
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{
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const re = /(\$\d{1,2})+(?:[\D]|\b)/g;
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assert(replaceText.match(re).length >= 3);
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}
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```
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# --seed--
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## --seed-contents--
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```js
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let str = "one two three";
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let fixRegex = /change/; // Change this line
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let replaceText = ""; // Change this line
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let result = str.replace(fixRegex, replaceText);
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```
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# --solutions--
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```js
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let str = "one two three";
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let fixRegex = /(\w+) (\w+) (\w+)/g; // Change this line
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let replaceText = "$3 $2 $1"; // Change this line
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let result = str.replace(fixRegex, replaceText);
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```
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