144 lines
6.9 KiB
Markdown
144 lines
6.9 KiB
Markdown
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---
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title: Diff Two Arrays
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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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Check two arrays and return a new array that contains only the items that are not in either of the original arrays.
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#### Relevant Links
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* <a href='https://devdocs.io/javascript/statements/for' target='_blank' rel='nofollow'>for Loop (Devdocs)</a>
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* <a href='https://devdocs.io/javascript/global_objects/array/includes' target='_blank' rel='nofollow'>Array.prototype.includes (Devdocs)</a>
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* <a href='https://devdocs.io/javascript/global_objects/array/filter' target='_blank' rel='nofollow'>Array.prototype.filter (Devdocs)</a>
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* <a href='https://devdocs.io/javascript/global_objects/array/concat' target='_blank' rel='nofollow'>Array.prototype.concat (Devdocs)</a>
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##  Hint: 1
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Merge the list to make it easy to compare functions.
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> _try to solve the problem now_
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##  Hint: 2
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Use filter to get the new array, you will need to create a callback function.
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> _try to solve the problem now_
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##  Hint: 3
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The best way to go about the callback function is to check if the number from the new merged array is not in **both** original arrays and return it.
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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 (Imperative Solution):
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```javascript
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function diffArray(arr1, arr2) {
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var newArr = [];
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function onlyInFirst(first, second) {
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// Looping through an array to find elements that don't exist in another array
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for (var i=0;i<first.length;i++) {
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if (second.indexOf(first[i]) === -1) {
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// Pushing the elements unique to first to newArr
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newArr.push(first[i]);
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}
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}
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}
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onlyInFirst(arr1, arr2);
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onlyInFirst(arr2, arr1);
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return newArr;
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}
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diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);
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```
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 <a href="https://repl.it/CLme/0">Run Code</a>
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### Code Explanation:
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Read the comments in the code.
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#### Relevant Links
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* <a href='https://devdocs.io/javascript/statements/for' target='_blank' rel='nofollow'>for Loop (Devdocs)</a>
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##  Intermediate Code Solution (Declarative Solution):
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```javascript
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function diffArray(arr1, arr2) {
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return arr1
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.concat(arr2)
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.filter(
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item => !arr1.includes(item) || !arr2.includes(item)
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)
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}
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diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);
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```
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 <a href="https://repl.it/CNYb/0">Run Code</a>
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### Code Explanation:
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Explain solution here and add any relevant links
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#### Relevant Links
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* <a href='https://devdocs.io/javascript/global_objects/array/concat' target='_blank' rel='nofollow'>Array.prototype.concat (Devdocs)</a>
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* <a href='https://devdocs.io/javascript/global_objects/array/filter' target='_blank' rel='nofollow'>Array.prototype.filter (Devdocs)</a>
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* <a href='https://devdocs.io/javascript/global_objects/array/includes' target='_blank' rel='nofollow'>Array.prototype.includes (Devdocs)</a>
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##  Advanced Code Solution (Declarative Solution):
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function diffArray(arr1, arr2) {
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return arr1
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.filter(el => !arr2.includes(el))
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.concat(
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arr2.filter(el => !arr1.includes(el))
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)
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}
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diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);
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 <a href="https://repl.it/CNYU/0">Run Code</a>
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### Code Explanation:
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Explain solution here and add any relevant links
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##  Advanced Code Solution Alternative (Declarative Solution):
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function diffArray(arr1, arr2) {
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return [
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...diff(arr1, arr2),
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...diff(arr2, arr1)
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]
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function diff(a, b) {
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return a.filter(item => b.indexOf(item) === -1);
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}
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}
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#### Relevant Links
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* <a href='https://devdocs.io/javascript/global_objects/array/includes' target='_blank' rel='nofollow'>Array.prototype.includes (Devdocs)</a>
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* <a href='https://devdocs.io/javascript/global_objects/array/filter' target='_blank' rel='nofollow'>Array.prototype.filter (Devdocs)</a>
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* <a href='https://devdocs.io/javascript/global_objects/array/concat' target='_blank' rel='nofollow'>Array.prototype.concat (Devdocs)</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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