8000 add caesar cipher · schoettker/javascript-exercises@b847c3b · GitHub
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add caesar cipher
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‎README.md

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@@ -13,8 +13,6 @@ The first exercise, `helloWorld` will walk you through the process in more depth
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## planned exercises (in no particular order for the moment):
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1. book titles (MC)
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1. leap years
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1. Caesar Cipher
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1. Palindromes
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1. Pangrams
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1. pig latin (MC)

‎caesar/README.md

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# Exercise XX - caesar cipher
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Implement the legendary caesar cipher:
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> 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.
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write a function that takes a string to be encoded and a shift factor and then returns the encoded string:
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```javascript
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caesar('A', 1) // simply shifts the letter by 1: returns 'B'
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```
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the cipher should retain capitalization:
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```javascript
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caesar('Hey', 5) // returns 'Mjd;
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```
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should _not_ shift punctuation:
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```javascript
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caesar('Hello, World!', 5) //returns 'Mjqqt, Btwqi!'
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```
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the shift should wrap around the alphabet:
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```javascript
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caesar('Z', 1) // returns 'A'
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```
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negative numbers should work as well:
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```javascript
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caesar('Mjqqt, Btwqi!', -5) // returns 'Hello, World!'
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```
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‎caesar/caesar.js

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var caesar = function() {
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}
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module.exports = caesar

‎caesar/caesar.spec.js

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var caesar = require('./caesar')
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describe('caesar', function() {
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it('works with single letters', function() {
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expect(caesar('A', 1)).toEqual('B');
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});
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xit('works with words', function() {
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expect(caesar('Aaa', 1)).toEqual('Bbb');
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});
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xit('works with phrases', function() {
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expect(caesar('Hello, World!', 5)).toEqual('Mjqqt, Btwqi!');
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});
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xit('works with negative shift', function() {
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expect(caesar('Mjqqt, Btwqi!', -5)).toEqual('Hello, World!');
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});
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xit('wraps', function() {
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expect(caesar('Z', 1)).toEqual('A');
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});
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xit('works with large shift factors', function() {
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expect(caesar('Hello, World!', 75)).toEqual('Ebiil, Tloia!');
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});
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});

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