Tryit Editor v2.9

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<!DOCTYPE html>
<html>
<body>

<p>The push method returns the new array length.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
var fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits;

function myFunction() {
    document.getElementById("demo").innerHTML = fruits.push("Kiwi");
}
</script>

</body>
</html>