return

break

switch

continue

throw

if...else

switch

case case

try...catch

var

let

const

using

const

await using

const

function

function*

async function

async function*

class

do...while

1

for

3

for...in

for...of

()

for await...of

while

JavaScript 1

0 1

debugger

export

import

import defer

import source

break continue

with

JavaScript ()()MDN__ 2

• let
• const
• using
• await using
• function
• function*
• async function
• async function*
• class
• export :
• import :

JavaScript if...else

if ()
  1;
else
  2;

SyntaxError let if

if ()
  let i = 0; // SyntaxError: Lexical declaration cannot appear in a single-statement context

var if

if ()
  var i = 0;

var var var

label: const a = 1; // SyntaxError: Lexical declaration cannot appear in a single-statement context

label: {
  const a = 1;
}

if () {
  let i = 0;
}

JavaScript eval() ()

if () const x =

JavaScript

• if () { ; }
• function x() { ; } const x =
• () => { ; } console.log()

JavaScript 1