This is what I tried below but I can't figure this one out?

I tried several different approaches and seems like I'm missing a small piece of code to figure it out. I was thinking maybe to us If and break when it doesn't equal A and equals D but then how would I count in the array when this happened?

const testing = [`aTest`, ` aFun`, `aYay`, `      dFun  `, ,];

let firstLetterChangeAToD;
let firstLetter;
let testingArrayWord;
let largestWord;

for (let i = 0; i <= Object.keys(testing).length; i++) {
    testingArrayWord = testing[`${i}`].trim();
    firstLetter = testingArrayWord.charAt(0);
    console.log(firstLetter);
}