JSFiddle - React, Tailwind, and code Playground

JavaScript

const s = '07:05:45PM';

const [hour, minute, second] = s.slice(0,8).split(':');

hour = s.includes('PM') ?
    (hour == 12 ? '12' : Number(hour) + 12) :
    (hour == 12 ? '00' : hour);

return `${hour}:${minute}:${second}`;