JSFiddle - React, Tailwind, and code Playground

HTML

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<img data-mobile="images/mobile.jpg" data-desktop="images/desktop.jpg" src="" alt="">

JavaScript

$(window).on('load', function() {
	var mobile = $('img').attr('data-mobile');
  var desktop = $('img').attr('data-desktop');
  if ( $(window).width() > 768 ) {
  	$('img').attr('src', desktop);
  } else {
  	$('img').attr('src', mobile);
  }
});