JSFiddle - React, Tailwind, and code Playground

JavaScript

var pageFunctions = {
    thing_page: function() {
        // Code for thing_page
        $('#thing_page input.finder').focus(function(){...});
    },
    other_page: function() {
        // Code for other_page
    },
    third_page: function() {
        // Code for third_page
    }
};

// Now call the correct function, according to the body ID
pageFunctions[ $(body)[0].id ]();