JSFiddle - React, Tailwind, and code Playground

HTML

<p id="tweet1">First long text displayed fully on hover</p>

<span class="tweet1">Second long text displayed fully on hover</span><br><br>

<span class="tweet1">Third long text displayed fully on hover</span>

CSS

#tweet1 {
    overflow:hidden;
    white-space:nowrap;
    width:120px;
}
.hiding {
    text-overflow:ellipsis;
}

JavaScript

var tweet = document.getElementById('tweet1');
tweet.id = 'tweet1';
tweet.className = 'hiding';

var slide_timer,
    max = tweet.scrollWidth,
    slide = function () {
        tweet.scrollLeft += 2;
        if (tweet.scrollLeft < max) {
            slide_timer = setTimeout(slide, 40);
        }
    };

tweet.onmouseover = tweet.onmouseout = function (e) {
    e = e || window.event;
    e = e.type === 'mouseover';
    clearTimeout(slide_timer);
    tweet.className = e ? '' : 'hiding';
    if (e) {
        slide();
    } else {
        tweet.scrollLeft = 0;
    }
};