JSFiddle - React, Tailwind, and code Playground

HTML

<h1 class="title-case">You Are a the Coolest</h1>

<h1 class="title-case">Hey You! <span>You are the Coolest!</span></h1>

CSS

h1 {
    font-size: 24px;
}

.title-case {
    text-transform: uppercase;
}

.first-letter {
    font-size: 115%;
}

JavaScript

$('.title-case').each(function(){
    $(this).html( capitalize_first_letter( $(this).html() ) );
});


function capitalize_first_letter( str ) {
    var words = str.split(' ');
    var html = '';
    $.each(words, function() {
        var first_letter = this.substring(0,1);
        html += ( first_letter == first_letter.toUpperCase() ? '<span class="first-letter">'+first_letter+'</span>' : first_letter )+this.substring(1) + ' ';
    });
    return html;
}