JSFiddle - React, Tailwind, and code Playground

HTML

<div class="test">first test</div><br />
<div class="test">second test</div><br />
<div class="test">third test</div><br />
<div class="test">fourth test</div><br />

JavaScript

$.fn.capitalise = function() {
    return this.each(function() {
        var $this = $(this),
            text = $this.text(),
            tokens = text.split(" ").filter(function(t) {return t != ""; }),
            res = [],
            i,
            len,
            component;
        for (i = 0, len = tokens.length; i < len; i++) {
            component = tokens[i];
            res.push(component.substring(0, 1).toUpperCase());
            res.push(component.substring(1));
            res.push(" "); // put space back in
        }
        $this.text(res.join(""));
    });
};

$(".test").capitalise();