disable in css code example

Example 1: disable whole div bootstrap 4

$("#mydiv").addClass("disabledbutton");
.disabledbutton {
    pointer-events: none;
    opacity: 0.4;
}

Example 2: css disabled

<input type="text" name="username" value="admin" >

<style type="text/css">
input[name=username] {
    pointer-events: none;
 }
</style>