temporary dead zone

TDZ.js

// ---------------------------------------------------------------------
// 1. UNCONTROVERSIAL AMONGST TC39
// ---------------------------------------------------------------------

// read before write throws
{
    console.log(x); // throws
    let x = 12;
    console.log(x);
}

// functions are initialized on entry to block
{
    console.log(f); // prints function
    function f() { }
}

// read before write throws even if it syntactically looks like the
// assignment happens before any read
{
    f(); // throws
    let x = 12;
    function f() { return x } // tries to read local x
}

// read before write throws even if there's all sorts of crazy control
// flow that makes it totally unclear syntactically whether that's going
// to happen; hence the term "temporal" -- the variable is dead for the
// time period between when it's in scope and when it's first initialized
{
    // might or might not call f
    function helper(callback) {
        if (Math.random() < 0.5) {
            return callback();
        }
        return "didn't feel like calling the callback";
    }

    {
        helper(f); // throws iff helper calls f
        let x = 12;
        function f() { return x; } // tries to read local x
    }
}

// ----------------------------------------------------------------------
// 2. CONTROVERSIAL, i.e., DAVE HATES IT :)
// ----------------------------------------------------------------------

// *only* allowed to be initialized with the syntactic initializer
{
    x = "initialized"; // throws
    let x = "foobar";
}

// legal:
{
    let x = foo() ? bar() : baz();
}

// illegal:
{
    let x;
    if (foo()) {
        x = bar(); // throws
    } else {
        x = baz(); // throws
    }
}

{
    let x;
    if (foo()) {
        x = bar(); // throws
    } else {
        x = baz(); // throws
    }
}

throws????

I know this throws

{
    if (foo()) {
      let  x = bar(); // throws
    } else {
       let x = baz(); // throws
    }
console.log(x)
}

{
    let x;
    if (foo()) {
        x = bar(); // throws
    } else {
        x = baz(); // throws
    }
}

throws????

I know this throws

{
    if (foo()) {
      let  x = bar(); // throws
    } else {
       let x = baz(); // throws
    }
console.log(x)
}