filter map problem

filter returning empty cannot be acted upon by chained map

HTML

<div>
letters = ["a", "b", "c"]
</div>
<div>
const numbers = [1, 2, 3]
</div>
<div><span>Result:</span>
<span id="p">
...click a button
</span>
</div><br>
<button onClick=(result(letters))>look for "a" in letters</button>
<button onClick=(result(numbers))>look for "a" in numbers</button>

JavaScript

const letters = ["a", "b", "c"];

const numbers = [1, 2, 3]

function result (arr) {

arr.filter((x) => {return x === "a"}).map((y, i, arr) => {

if(arr.length === 0) {
return (document.getElementById("p").innerHTML = "empty")
} else {
return (document.getElementById("p").innerHTML = "found it")
}})
}