<script>
function findWord(){
var paragraph = document.getElementById('paragraph').textContent;

var searchTerm = document.getElementById('Text').value;
var indexOfFirst = paragraph.indexOf(searchTerm);
var indexOfSecond = paragraph.indexOf(searchTerm, (indexOfFirst + 1));

console.log(indexOfFirst);

console.log(indexOfSecond);
}

function selectFoundWord() {
    var paragraph = document.getElementById("paragraph");
    paragraph.setSelectionRange(indexOfFirst); // Highlights
    paragraph.focus();
}
</script>
    <input type="text" id='Text' placeholder="Inserire input" >
    <button onclick="findWord();selectFoundWord()">Input</button>

    <style>
    textarea {
    width: 210px;
    height: 100px;
    }

    </style>
    <div>
    <textarea id="paragraph"> Lorem ipsum dolor sit amet consectetur adipisicing elit. Odio dignissimos dolor, aperiam est labore unde tenetur totam voluptatum aliquid harum molestias reprehenderit perspiciatis dolore fugit iusto libero facere, voluptates tempore debitis a earum quod omnis similique. Quidem molestias commodi sunt illo odit ea vitae, reiciendis ad nisi aut asperiores tenetur deleniti architecto, animi libero voluptatem soluta similique ipsum repellendus repudiandae. </textarea>
    </div>