<!DOCTYPE html>
<html>
<head>
<style>
#main {
width: 250px;
height: 100px;
border: 1px solid #c3c3c3;
display: flex;
}
#main div {
flex: 0 0 50px;
}
</style>
</head>
<body>
<h1>Change flex with JavaScript</h1>
<div id="main">
<div style="background-color:coral;">Red DIV</div>
<div style="background-color:lightblue;" id="myBlueDiv">Blue DIV</div>
</div>
<p>Click the "Try it" button to set the value of the flex property to "200px" for the blue div element</p>
<button onclick="myFunction()">Try it</button>
<script>
function myFunction() {
document.getElementById("myBlueDiv").style.flex = "0 0 200px";
}
</script>
</body>
</html>