TheSanches,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script>
"use strict"
window.addEventListener('DOMContentLoaded', function() {
function myFunc(){
let arr = ['один', 'два', 'три', 'четыре', 'пять'];
let input = document.getElementById('input').value; //получаем значение введенное в input
let out = document.getElementById('out');
let assessment = false;
for(let i = 0; i < arr.length; i++){
if(arr[i] == input){
assessment = true; break;
}
}
out.innerHTML = assessment
}
document.getElementById('enter').addEventListener('click', myFunc);
});
</script>
</head>
<body>
<input type="text" id="input" value="три">
<button id="enter">Click</button>
<p id="out"></p>
</body>
</html>