JSFiddle - React, Tailwind, and code Playground

HTML

<img src="/Content/Images/Icons/Theme1/title.png" class="slideExampleImage">
<img src="/Content/Images/Icons/Theme1/test.png" class="slideExampleImage">
<img src="/Content/Images/Icons/Theme1/bill.png" class="slideExampleImage">

JavaScript

function changeTheme(newTheme) {
  $(".slideExampleImage").attr("src", function(_, oldSrc) {
    var parts = oldSrc.split(/\//);

    parts.splice(parts.length - 2, 1, newTheme);
		console.log(parts.join("/"));

    return parts.join("/");
  });
}

changeTheme("foo");