JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    MAR/26/2013
</div>
<div>
    JAN/25/2011
</div>
<div>
    FEB/8/2032
</div>
<div>
    JUL/6/1987
</div>
<div>
    DEC/24/2014
</div>
<div>
    Hel/lo/world
</div>

JavaScript

$("div").each(function() {
    // convert month abbreviation to numerical representation
    var el = $(this);
    var monthStr = el.text().match(/[^\/]*/)[0].trim();        
    var months = {
        JAN: 1,
        FEB: 2,
        MAR: 3,
        APR: 4,
        MAY: 5,
        JUN: 6,
        JUL: 7,
        AUG: 8,
        SEP: 9,
        OCT: 10,
        NOV: 11,
        DEC: 12
    };
    var month = (months[monthStr]) ? months[monthStr].toString() : monthStr;
    el.text(el.text().replace(monthStr, month));
});