zig Tryit Editor

<!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>

</body>

</html>