Add "Make a function that does arithmetic!" kata

Author: juanantonioledesma

7-kyu/make-a-function-that-does-arithmetic.md

@@ -0,0 +1,55 @@
+<h1>Make a function that does arithmetic! <sup><sup>7 Kyu</sup></sup></h1>
+
+<sup>
+  <a href="https://www.codewars.com/kata/583f158ea20cfcbeb400000a">
+    <strong>LINK TO THE KATA</strong>
+  </a> - <code>FUNDAMENTALS</code>
+</sup>
+
+## Description
+
+Given two numbers and an arithmetic operator (the name of it, as a string), return the result of the two numbers having that operator used on them.
+
+`a` and `b` will both be positive integers, and `a` will always be the first number in the operation, and b always the second.
+
+The four operators are "add", "subtract", "divide", "multiply".
+
+A few **examples:(Input1, Input2, Input3 --> Output)**
+
+```
+5, 2, "add"      --> 7
+5, 2, "subtract" --> 3
+5, 2, "multiply" --> 10
+5, 2, "divide"   --> 2.5
+```
+
+Try to do it without using if statements!
+
+## Solutions
+
+```javascript
+const arithmetic = (a, b, operator) => {
+  const operations = {
+    add: a + b,
+    subtract: a - b,
+    multiply: a * b,
+    divide: a / b,
+  }
+
+  return operations[operator]
+}
+```
+
+---
+
+```javascript
+const arithmetic = (a, b, operator) => {
+  return operator === 'add'
+    ? a + b
+    : operator === 'subtract'
+    ? a - b
+    : operator === 'multiply'
+    ? a * b
+    : a / b
+}
+```

README.md

@@ -117,6 +117,7 @@ JavaScript katas on Codewars are programming challenges that help you improve yo
 - **[Isograms](./7-kyu/isograms.md)**<br><sup>`STRINGS` `FUNDAMENTALS`</sup>
 - **[L2: Triple X](./7-kyu/l2-triple-x.md)**<br><sup>`STRINGS` `REGULAR EXPRESSIONS` `FUNDAMENTALS`</sup>
 - **[Letterbox Paint-Squad](./7-kyu/letterbox-paint-squad.md)**<br><sup>`FUNDAMENTALS`</sup>
+- **[Make a function that does arithmetic!](./7-kyu/make-a-function-that-does-arithmetic.md)**<br><sup>`FUNDAMENTALS`</sup>
 - **[Merge two arrays](./7-kyu/merge-two-arrays.md)**<br><sup>`FUNDAMENTALS` `ARRAYS`</sup>
 - **[Return the closest number multiple of 10](./7-kyu/return-the-closest-number-multiple-of-10.md)**<br><sup>`MATHEMATICS` `FUNDAMENTALS`</sup>
 - **[Sort Numbers](./7-kyu/sort-numbers.md)**<br><sup>`FUNDAMENTALS`</sup>