add icon before span css code example

Example 1: how to insert icons pseudo content

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

Example 2: 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>