JSFiddle - React, Tailwind, and code Playground

HTML

<div class="sunday">Sunday</div>
<div class="monday">Monday</div>
<div class="tuesday">Tuesday</div>
<div class="wednesday">Wednesday</div>
<div class="thursday">Thursday</div>
<div class="friday">Friday</div>
<div class="saturday">Saturday</div>

JavaScript

$(window).resize(function() {
    if ($(window).width() < 950) {
        $( "div.sunday" ).replaceWith( "S" );
        $( "div.monday" ).replaceWith( "M" );
        $( "div.tuesday" ).replaceWith( "T" );
        $( "div.wednesday" ).replaceWith( "W" );
        $( "div.thursday" ).replaceWith( "T" );
        $( "div.friday" ).replaceWith( "F" );
        $( "div.saturday" ).replaceWith( "S" );
    }
}