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