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cdfa264b33
* chore: added helper variable * feat: added new rotation option * Revert "chore: added helper variable" This reverts commit 489544da0a3d479910fbea020d3be3d0d10681bf.
33 lines
1.4 KiB
JavaScript
33 lines
1.4 KiB
JavaScript
/**
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* @function caesarsCipher
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* @description - 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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* @see - [wiki](https://en.wikipedia.org/wiki/Caesar_cipher)
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* @param {string} str - string to be encrypted
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* @param {number} rotation - the number of rotation, expect real number ( > 0)
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* @return {string} - decrypted string
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*/
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const caesarsCipher = (str, rotation) => {
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if (typeof str !== 'string' || !Number.isInteger(rotation) || rotation < 0) {
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throw new TypeError('Arguments are invalid')
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}
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const alphabets = new Array(26)
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.fill()
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.map((_, index) => String.fromCharCode(97 + index)) // generate all lower alphabets array a-z
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const cipherMap = alphabets.reduce(
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(map, char, index) => map.set(char, alphabets[(rotation + index) % 26]),
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new Map()
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)
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return str.replace(/[a-z]/gi, (char) => {
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if (/[A-Z]/.test(char)) {
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return cipherMap.get(char.toLowerCase()).toUpperCase()
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}
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return cipherMap.get(char)
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})
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}
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export default caesarsCipher
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