First and Last Index

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

Examples

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

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

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

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

Notes

• 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.