JSFiddle - React, Tailwind, and code Playground

JavaScript

if (!window.myFunction) {
    window.myFunction = function() {
        alert("Func");
    }
    alert("Declared Func");
}
if (!window.myFunction) {
    window.myFunction = function() {
        alert("Func");
    }
    alert("Declared Func");
}

myFunction();