a539c1776a
Technically, the % operator in JS is _not_ the modulo operator. It's a different operator that returns negative values by design. So it _does_ work with negative numbers as intended, it's just not the operator that is needed for the caesar shift. Therefore, mod does not "make % work with negative numbers", it just uses % to implement the modulo operator. The previous comment might suggest that there is a bug that gets fixed, the new comment hopefully avoids that source of possible confusion. |
||
|---|---|---|
| .. | ||
| .DS_Store | ||
| README.md | ||
| caesar.js | ||
| caesar.spec.js | ||
README.md
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:
caesar('A', 1) // simply shifts the letter by 1: returns 'B'
the cipher should retain capitalization:
caesar('Hey', 5) // returns 'Mjd;
should not shift punctuation:
caesar('Hello, World!', 5) //returns 'Mjqqt, Btwqi!'
the shift should wrap around the alphabet:
caesar('Z', 1) // returns 'A'
negative numbers should work as well:
caesar('Mjqqt, Btwqi!', -5) // returns 'Hello, World!'