27 lines
733 B
JavaScript
27 lines
733 B
JavaScript
const caesar = function(string, shift) {
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return string
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.split("")
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.map(char => shiftChar(char, shift))
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.join("");
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};
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const codeSet = code => (code < 97 ? 65 : 97);
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// this function is just a fancy way of doing % so that it works with negative numbers
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// see this link for details:
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// https://stackoverflow.com/questions/4467539/javascript-modulo-gives-a-negative-result-for-negative-numbers
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const mod = (n, m) => (n % m + m) % m;
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const shiftChar = (char, shift) => {
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const code = char.charCodeAt();
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if ((code >= 65 && code <= 90) || (code >= 97 && code <= 122)) {
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return String.fromCharCode(
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mod(code + shift - codeSet(code), 26) + codeSet(code)
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);
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}
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return char;
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};
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module.exports = caesar;
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