Rename folders with numbers and underscores

13_caesar/README.md

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+# Exercise 13 - Caesar cipher
+
+Implement the legendary Caesar cipher:
+
+> In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.
+
+Hint: You may need to convert letters to their unicode values. Be sure to read the documentation!
+
+write a function that takes a string to be encoded and a shift factor and then returns the encoded string:
+
+```javascript
+caesar('A', 1) // simply shifts the letter by 1: returns 'B'
+```
+
+the cipher should retain capitalization:
+```javascript
+caesar('Hey', 5) // returns 'Mjd;
+```
+
+should _not_ shift punctuation:
+```javascript
+caesar('Hello, World!', 5) //returns 'Mjqqt, Btwqi!'
+```
+
+the shift should wrap around the alphabet:
+```javascript
+caesar('Z', 1) // returns 'A'
+```
+
+negative numbers should work as well:
+```javascript
+caesar('Mjqqt, Btwqi!', -5) // returns 'Hello, World!'
+```

13_caesar/caesar.js

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+const caesar = function() {
+
+};
+
+module.exports = caesar;

13_caesar/caesar.spec.js

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+const caesar = require('./caesar')
+
+test('works with single letters', () => {
+  expect(caesar('A', 1)).toBe('B');
+});
+test.skip('works with words', () => {
+  expect(caesar('Aaa', 1)).toBe('Bbb');
+});
+test.skip('works with phrases', () => {
+  expect(caesar('Hello, World!', 5)).toBe('Mjqqt, Btwqi!');
+});
+test.skip('works with negative shift', () => {
+  expect(caesar('Mjqqt, Btwqi!', -5)).toBe('Hello, World!');
+});
+test.skip('wraps', () => {
+  expect(caesar('Z', 1)).toBe('A');
+});
+test.skip('works with large shift factors', () => {
+  expect(caesar('Hello, World!', 75)).toBe('Ebiil, Tloia!');
+});
+test.skip('works with large negative shift factors', () => {
+  expect(caesar('Hello, World!', -29)).toBe('Ebiil, Tloia!');
+});