let

let x = 1;

if (x === 1) {
  let x = 2;

  console.log(x);
  // : 2
}

console.log(x);
// : 1

let name1;
let name1 = value1;
let name1 = value1, name2 = value2;
let name1, name2 = value2;
let name1 = value1, name2, /* , */ nameN = valueN;

{
  // TDZ 
  console.log(bar); // "undefined"
  console.log(foo); // ReferenceError: Cannot access 'foo' before initialization
  var bar = 1;
  let foo = 2; // TDZ foo 
}

{
  // TDZ 
  const func = () => console.log(letVar); // OK

  // TDZ letVar  `ReferenceError` 

  let letVar = 3; // TDZ letVar 
  func(); // TDZ 
}

{
  typeof i; // ReferenceError: Cannot access 'i' before initialization
  let i = 10;
}

console.log(typeof undeclaredVariable); // "undefined"

{
  let foo;
  let foo; // SyntaxError: Identifier 'foo' has already been declared
}

function foo(a) {
  let a = 1; // SyntaxError: Identifier 'a' has already been declared
}
try {
} catch (e) {
  let e; // SyntaxError: Identifier 'e' has already been declared
}

let x = 1;

switch (x) {
  case 0:
    let foo;
    break;
  case 1:
    let foo; // SyntaxError: Identifier 'foo' has already been declared
    break;
}

let x = 1;

switch (x) {
  case 0: {
    let foo;
    break;
  }
  case 1: {
    let foo;
    break;
  }
}

function varTest() {
  var x = 1;
  {
    var x = 2; // !
    console.log(x); // 2
  }
  console.log(x); // 2
}

function letTest() {
  let x = 1;
  {
    let x = 2; // 
    console.log(x); // 2
  }
  console.log(x); // 1
}

var x = "global";
let y = "global";
console.log(this.x); // "global"
console.log(this.y); // undefined

function test() {
  var foo = 33;
  if (foo) {
    let foo = foo + 55; // ReferenceError
  }
}
test();

function go(n) {
  // n 
  console.log(n); // { a: [1, 2, 3] }

  for (let n of n.a) {
    //          ^ ReferenceError
    console.log(n);
  }
}

go({ a: [1, 2, 3] });

var a = 1;
var b = 2;

{
  var a = 11; // 
  let b = 22; //  if 

  console.log(a); // 11
  console.log(b); // 22
}

console.log(a); // 11
console.log(b); // 2

let x = 1;

{
  var x = 2; //  SyntaxError
}

const result = /(a+)(b+)(c+)/.exec("aaabcc");
let [, a, b, c] = result;
console.log(a, b, c); // "aaa" "b" "cc"