Algorithms and Data Structures implemented in JavaScript for beginners, following best practices.
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/**
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* @function countLetters
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* @description Given a string, count the number of each letter.
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* @param {String} str - The input string
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* @return {Object} - Object with letters and number of times
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* @example countLetters("hello") => {h: 1, e: 1, l: 2, o: 1}
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*/
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const countLetters = (str) => {
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const specialChars = /\W/g
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if (typeof str !== 'string') {
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throw new TypeError('Input should be a string')
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}
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if (specialChars.test(str)) {
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throw new TypeError('Input must not contain special characters')
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}
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if (/\d/.test(str)) {
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throw new TypeError('Input must not contain numbers')
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}
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const obj = {}
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for (let i = 0; i < str.toLowerCase().length; i++) {
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const char = str.toLowerCase().charAt(i)
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obj[char] = (obj[char] || 0) + 1
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}
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return obj
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}
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export { countLetters }
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