<!DOCTYPE html>
<html>
<head>
<style>
.item3 { grid-column: auto / span 2; }
.grid-container {
display: grid;
grid-template-columns: auto auto auto;
grid-template-rows: auto auto;
grid-auto-flow: row;
grid-gap: 10px;
background-color: #2196F3;
padding: 10px;
}
.grid-container > div {
background-color: rgba(255, 255, 255, 0.8);
text-align: center;
padding: 20px 0;
font-size: 30px;
}
</style>
</head>
<body>
<h1>Change the grid-auto-flow Property with JavaScript</h1>
<p>Click the button to set the grid-auto-flow to "row dense":</p>
<p><button onclick="myFunction()">Fill the hole</button></p>
<div class="grid-container" id="myDIV">
<div class="item1">1</div>
<div class="item2">2</div>
<div class="item3">3</div>
<div class="item4">4</div>
</div>
<script>
function myFunction() {
document.getElementById("myDIV").style.gridAutoFlow = "row dense";