When a value is added in an input box, then the oninput event occurs. You can try to run the following code to learn how to implement oninput event in JavaScript −
Example
<!DOCTYPE html>
<html>
<body>
<p>Write below:</p>
<input type = "text" id = "newInput" oninput = "inputFunc()">
<p id = "demo"></p>
<script>
function inputFunc() {
var a = document.getElementById("newInput").value;
document.write("Typed: " + a);
}
</script>
</body>
</html>