JSFiddle - React, Tailwind, and code Playground

by Fabio Dan

JavaScript

// Given a word, write a function that returns the first index and the 
// last index of a character.

// If the character does not exist in the word, return undefined.

// If only one instance of the character exists, the first and last index 
// will be the same.

const charIndex = (word, char) => word.includes(char) ? [word.indexOf(char), word.lastIndexOf(char)] : undefined

console.log(charIndex("hello", "l"))// ➞ [2, 3]
// The first "l" has index 2, the last "l" has index 3.

console.log(charIndex("circumlocution", "c"))// ➞ [0, 8]
// The first "c" has index 0, the last "c" has index 8.

console.log(charIndex("happy", "h"))// ➞ [0, 0]
// Only one "h" exists, so the first and last index is 0.

console.log(charIndex("happy", "e"))// ➞ undefined
// "e" does not exist in "happy", so we return undefined.