124 lines
7.0 KiB
Markdown
124 lines
7.0 KiB
Markdown
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---
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title: Spinal Tap Case
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---
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 Remember to use <a>**`Read-Search-Ask`**</a> if you get stuck. Try to pair program  and write your own code 
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###  Problem Explanation:
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Convert the given string to a lowercase sentence with words joined by dashes.
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#### Relevant Links
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* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String' target='_blank' rel='nofollow'>String global object</a>
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* <a>JS Regex Resources</a>
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* <a href='http://forum.freecodecamp.com/t/javascript-string-prototype-replace/15942' target='_blank' rel='nofollow'>JS String Prototype Replace</a>
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* <a href='http://forum.freecodecamp.com/t/javascript-string-prototype-tolowercase/15948' target='_blank' rel='nofollow'>JS String Prototype ToLowerCase</a>
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##  Hint: 1
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Create a regular expression for all white spaces and underscores.
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> _try to solve the problem now_
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##  Hint: 2
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You will also have to make everything lowercase.
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> _try to solve the problem now_
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##  Hint: 3
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The tricky part is getting the regular expression part to work, once you do that then just turn the uppercase to lowercase and replace spaces with underscores using `replace()`.
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> _try to solve the problem now_
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## Spoiler Alert!
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**Solution ahead!**
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##  Basic Code Solution:
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function spinalCase(str) {
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// Create a variable for the white space and underscores.
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var regex = /\s+|_+/g;
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// Replace low-upper case to low-space-uppercase
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str = str.replace(/([a-z])([A-Z])/g, '$1 $2');
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// Replace space and underscore with -
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return str.replace(regex, '-').toLowerCase();
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}
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// test here
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spinalCase('This Is Spinal Tap');
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 <a href='https://repl.it/CLnS/0' target='_blank' rel='nofollow'>Run Code</a>
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### Code Explanation:
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* **regex** contains the regular expression `/\s+|_+/g`, which will select all white spaces and underscores.
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* The first `replace()` puts a space before any encountered uppercase characters in the string **str** so that the spaces can be replaced by dashes later on.
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* While returning the string, another `replace()` replaces spaces and underscores with dashes using **regex**.
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##  Intermediate Code Solution:
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function spinalCase(str) {
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// Replace low-upper case to low-space-uppercase
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str = str.replace(/([a-z])([A-Z])/g, '$1 $2');
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// Split on whitespace and underscores and join with dash
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return str.toLowerCase().split(/(?:_| )+/) .join('-');
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}
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// test here
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spinalCase('This Is Spinal Tap');
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 <a href='https://repl.it/CLnT/0' target='_blank' rel='nofollow'>Run Code</a>
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### Code Explanation:
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* Similar to the first solution, the first `replace()` puts a space before any encountered uppercase characters in the string **str** so that the spaces can be replaced by dashes later on.
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* Instead of using `replace()` here to replace whitespace and underscores with dashes, the string is `split()` on the regular expression `/(?:_| )+/` and `join()`-ed on `-`.
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#### Relevant Links
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* <a href='http://forum.freecodecamp.com/t/javascript-string-prototype-split/15944' target='_blank' rel='nofollow'>JS String Prototype Split</a>
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* <a href='http://forum.freecodecamp.com/t/javascript-array-prototype-join/14292' target='_blank' rel='nofollow'>JS Array Prototype Join</a>
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##  Advanced Code Solution:
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function spinalCase(str) {
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// "It's such a fine line between stupid, and clever."
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// --David St. Hubbins
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return str.split(/\s|_|(?=[A-Z])/).join('-').toLowerCase()
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}
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 <a href='https://repl.it/EUZV' target='_blank' rel='nofollow'>Run Code</a>
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### Code Explanation:
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* Split the string at one of the following conditions (_converted to an array_)
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* a whitespace character [`\s`] is encountered
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* underscore character [`_`] is encountered
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* or is followed by an uppercase letter [`(?=[A-Z])`]
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* Join the array using a hyphen (`-`)
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* Lowercase the whole resulting string
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#### Relevant Links
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* <a href='http://devdocs.io/javascript/global_objects/string/split' target='_blank' rel='nofollow'>String#split</a>
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* <a href='http://devdocs.io/javascript/global_objects/regexp' target='_blank' rel='nofollow'>RegExp</a>
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* <a href='http://devdocs.io/javascript/global_objects/array/join' target='_blank' rel='nofollow'>Arrray#join</a>
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* <a href='http://devdocs.io/javascript/global_objects/string/tolowercase' target='_blank' rel='nofollow'>String#toLowerCase</a>
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##  NOTES FOR CONTRIBUTIONS:
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*  **DO NOT** add solutions that are similar to any existing solutions. If you think it is **_similar but better_**, then try to merge (or replace) the existing similar solution.
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* Add an explanation of your solution.
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* Categorize the solution in one of the following categories — **Basic**, **Intermediate** and **Advanced**. 
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* Please add your username only if you have added any **relevant main contents**. ( **_DO NOT_** _remove any existing usernames_)
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> See  <a href='http://forum.freecodecamp.com/t/algorithm-article-template/14272' target='_blank' rel='nofollow'>**`Wiki Challenge Solution Template`**</a> for reference.
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