Sandbox::https://github.com/sibalonecoding-code/JavaScript/blob/master/String/FirstUniqueCharacter.js

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/**

* @function firstUniqChar

* @description Given a string str, find the first non-repeating character in it and return its index. If it does not exist, return -1.

* @param {String} str - The input string

* @return {Number} - The index of first unique character.

* @example firstUniqChar("javascript") => 0

* @example firstUniqChar("sesquipedalian") => 3

* @example firstUniqChar("aabb") => -1

const firstUniqChar = (str) => {

if (typeof str !== 'string') {

throw new TypeError('Argument should be string')

}

const count = new Map()

for (const char of str) {

if (!count[char]) {

count[char] = 1

} else {

count[char]++

}

for (let i = 0; i < str.length; i++) {

if (count[str[i]] === 1) return i

}

return -1

}

export { firstUniqChar }