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38 lines
1.1 KiB
JavaScript
38 lines
1.1 KiB
JavaScript
/**
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* Caesar's Cipher - also known as the ROT13 Cipher is when
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* a letter is replaced by the one that is 13 spaces away
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* from it in the alphabet. If the letter is in the first half
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* of the alphabet we add 13, if it's in the latter half we
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* subtract 13 from the character code value.
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*/
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/**
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* Decrypt a ROT13 cipher
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* @param {String} str - string to be decrypted
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* @return {String} decrypted string
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*/
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function rot13(str) {
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let response = [];
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let strLength = str.length;
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for (let i =0; i < strLength; i++) {
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const char = str.charCodeAt(i);
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if (char < 65 || (char > 90 && char < 97) || char > 122) {
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response.push(str.charAt(i));
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} else if ((char > 77 && char <= 90 ) || (char > 109 && char <= 122)) {
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response.push(String.fromCharCode(str.charCodeAt(i) - 13));
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} else {
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response.push(String.fromCharCode(str.charCodeAt(i) + 13));
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}
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}
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return response.join('');
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}
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// Caesars Cipher Example
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const encryptedString = 'Uryyb Jbeyq';
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const decryptedString = rot13(encryptedString);
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console.log(decryptedString); // Hello World
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