how to insert icons pseudo content

<div class="css">hard coded css content</div>
<div class="css char">hard coded css content char</div>
<br>
<div class="data red" data-icon="†">hard coded data-icon</div>
<div class="data blue" data-icon="†">hard coded data-icon char</div>
<br>
<div class="js red">data-icon by js</div>
<div class="js blue">data-icon by js char</div>

.css:after {
    content: "\86";
    color: red;
}
.css.char:after {
    content: "†";
    color: blue;
}
.data:after {
    content: attr( data-icon );
}
.js:after {
    content: attr( data-icon );
}
.red:after {
    color: red;
}
.blue:after {
    color: blue;
}

var js = document.querySelectorAll( ".js" );
js[ 0 ].setAttribute( "data-icon", "\u0086" );
js[ 1 ].setAttribute( "data-icon", "†" );