Use the flexShrink property to set how much the item will shrink relative to the rest with JavaScript.
Example
You can try to run the following code to learn how to work with flexGrow property −
<!DOCTYPE html>
<html>
<head>
<style>
#box {
border: 1px solid #000000;
width: 500px;
height: 100px;
display: flex;
}
#box div {
flex-grow: 1;
flex-shrink: 1;
flex-basis: 300px;
}
</style>
</head>
<body>
<div id = "box">
<div style = "background-color:orange;">DIV1</div>
<div style = "background-color:yellow;" id = "myID">DIV2</div>
</div>
<p>Using flexShrink property</p>
<button onclick = "display()">Set</button>
<script>
function display() {
document.getElementById("myID").style.flexShrink = "5";
}
</script>
</body>
</html>