String with the most letters

Given an array of strings, return the string which has the most letters.

Sample Code:

function mostLetters(arr) {
// Enter your logic here...
}

Examples:

Input: ['Javascript','Java','Python']
Output: 'Javascript'
Explanation: 'Javascript' has the most letters among all the elements.

Input: ['Web','Mobile','A.I','Data']
Output: 'Mobile'
Explanation: 'Mobile' has the most letters among all the elements.