JSFiddle - React, Tailwind, and code Playground

JavaScript

(function(){
    var a = 1;
    var b = 2;

    (function( ) { a = b; var b; })( );

    document.write('a:'+ a + "<br>");  // => "a:undefined"
    document.write('b:'+ b + "<br>");  // => "b:2"
})();