Variable scope in JavaScript: var, let, const and functions

Hello everyone! I just started learning JavaScript and I can't figure out variable scope. I'm writing simple code, but the results keep surprising me. Here's an example: ```javascript var x = 10; function test() { var x = 20; if (true) { var x = 30; console.log(x); // outputs 30 } console.log(x); // outputs 30, not 20! } test(); console.log(x); // outputs 10 ``` Why does the variable `x` change inside the `test()` function, even though I declared it with `var` inside the `if` block? I thought `var` was function-scoped, but here it behaves strangely. I've also heard about `let` and `const`, but I don't understand how they differ. Another example with closures: ```javascript for (var i = 0; i < 3; i++) { setTimeout(function() { console.l