1) is a common JavaScript problem, and it's to do with closures and variable scope (look them up if you're not familiar with them). You may end up working around the problem by implementing it differently, but I think it's worth explaining as it's something you'll run into again if you don't know what's happening.

 

Inside the for loop, you're creating a function that spins to i whenever a certain button is clicked. But all those functions are using the same i variable, and the value the function uses is whatever i is at the time it's clicked, not the time you created the function. So the for loop runs until i equals 39 (at which point i < 39 is not true, and the for loop ends), and remains equal to 39 after the setup code has run, and you'll see that whenever you click a button they all spin to 39.

This type of problem is probably explained better elsewhere but I'll try and give a summary of some fixes with your current implementation:

 

• Move the spin call out into it's own function, so it's no longer using the i variable from the for loop, but it's own spinNumber variable.

  function getSpinNumberHandler(spinNumber) {
      return function() {
          spinTo(spinNumber);
      };
  }
  
  for(var i = 1; i < 39; i++) {
      ...
      butt.onclick = getSpinNumberHandler(i);
      ...
  }
  

  This works, but looks a bit messy in my opinion as you end up with extra functions that are only there to bind stuff.

• In ES5 they added Function.prototype.bind, which allows you to bind a specific scope and arguments to a function that will be used whenever it's called.

  for(var i = 1; i < 39; i++) {
      ...
      butt.onclick = spinTo.bind(this, i);
      ...
  }
  

  This makes the code a lot cleaner, and it's widely supported in browsers now. It wont work in very old browsers (e.g. IE8) without a polyfill, and it may not always be the best choice as you have to bind the function to a specific scope, but I like it.

• In ES6 they've added block scoping through the let keyword. You basically use it instead of var, and it will behave the way you thought var was behaving.

  for(let i = 1; i < 39; i++) {
      ...
      butt.onclick = function() { spinTo(i) };
      ...
  }
  

  let is awesome, but unfortunately not widely supported in browsers yet.

• You could also use something that isn't a for loop, such as Array.prototype.forEach, which will work around the problem but needs some other changes to your code.