JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/ui-lightness/jquery-ui.css">
<div>
    <div>
        <div>The date is July 23</div>
        <div>some other text</div>
        <input value="123">
    </div>
    
    <div>The date is July 23, 1234</div>
    <div id='clicker'>some other text</div>
</div>

CSS

span { 
    background: yellow;
}

JavaScript

var regex = /(\d+)/g,
    replacement = '<span>$1</span>';

function replaceText(i,el) {
    if (el.nodeType === 3) {
        if (regex.test(el.data)) {
            $(el).replaceWith(el.data.replace(regex, replacement));
        }
    } else {
        $(el).contents().each( replaceText );
    }
}
        
$('body').each( replaceText );