JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="output" style="width: 99%; height: 20em; background-color: #ffc"></textarea>

JavaScript

// log() just writes a message to the text area
function log(message) {
    $('#output').val($('#output').val() + message + "\n");
}

// redefineFunction() will take a function reference and
// reassign it to a new function
function redefineFunction(f) {
    f = function(x) { return x * 3; };
}

// initial version of go()
function go(x) {
    return x;            
}

log(go(5)); // returns 5

// redefine go()
go = function(x) {
     return x * 2;        
}
    
log(go(5)); // returns 10

// redefine go() using redefineFunction()
redefineFunction(go);

log(go(5)); // returns 10, I want it to return 15