JSFiddle - React, Tailwind, and code Playground

HTML

<video autoplay loop width="960" height="540" id="video">
    <source src="http://clips.vorwaerts-gmbh.de/big_buck_bunny.ogv" id="tv_main_channel">
</video>

<pre id='program_source_mp4'>http://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4</pre> 
    
<button id='btn'>Click</button>
    
<pre id='output'>Src: http://clips.vorwaerts-gmbh.de/big_buck_bunny.ogv</pre>

CSS

#program_source_mp4 {
    display: none;
}

JavaScript

var btn = $('#btn');

btn.on('click', function () {
    var tv_main_channel = $('#tv_main_channel');
    var d_program_source_mp4 = $("#program_source_mp4").text();

    tv_main_channel.attr('src', d_program_source_mp4);
    
    
    var video_block = $('#video');
    video_block.load();
    
    
    $('#output').html("Src: " + d_program_source_mp4);    
});