Statements and declarations

JavaScript applications consist of statements with an appropriate syntax. A single statement may span multiple lines. Multiple statements may occur on a single line if each statement is separated by a semicolon. This isn't a keyword, but a group of keywords.

For an alphabetical listing see the sidebar on the left.

Block (en-US)

A block statement is used to group zero or more statements. The block is delimited by a pair of curly brackets.

break (en-US)

Terminates the current loop, switch, or label statement and transfers program control to the statement following the terminated statement.

continue (en-US)

Terminates execution of the statements in the current iteration of the current or labeled loop, and continues execution of the loop with the next iteration.

Empty (en-US)

An empty statement is used to provide no statement, although the JavaScript syntax would expect one.

if...else (en-US)

Executes a statement if a specified condition is true. If the condition is false, another statement can be executed.

switch (en-US)

Evaluates an expression, matching the expression's value to a case clause, and executes statements associated with that case.

throw (en-US)

Throws a user-defined exception.

try...catch (en-US)

Marks a block of statements to try, and specifies a response, should an exception be thrown.

var (en-US)

Declares a variable, optionally initializing it to a value.

let (en-US)

Declares a block scope local variable, optionally initializing it to a value.

const (en-US)

Declares a read-only named constant.

function (en-US)

Declares a function with the specified parameters.

function* (en-US)

Generators functions enable writing iterators more easily.

async function (en-US)

Declares an async function with the specified parameters.

return (en-US)

Specifies the value to be returned by a function.

class (en-US)

Declares a class.

do...while (en-US)

Creates a loop that executes a specified statement until the test condition evaluates to false. The condition is evaluated after executing the statement, resulting in the specified statement executing at least once.

for (en-US)

Creates a loop that consists of three optional expressions, enclosed in parentheses and separated by semicolons, followed by a statement executed in the loop.

for each...in

Iterates a specified variable over all values of object's properties. For each distinct property, a specified statement is executed.

for...in (en-US)

Iterates over the enumerable properties of an object, in arbitrary order. For each distinct property, statements can be executed.

for...of (en-US)

Iterates over iterable objects (including arrays, array-like objects, iterators and generators), invoking a custom iteration hook with statements to be executed for the value of each distinct property.

while (en-US)

Creates a loop that executes a specified statement as long as the test condition evaluates to true. The condition is evaluated before executing the statement.

debugger (en-US)

Invokes any available debugging functionality. If no debugging functionality is available, this statement has no effect.

export

Used to export functions to make them available for imports in external modules, another scripts.

import (en-US)

Used to import functions exported from an external module, another script.

label (en-US)

Provides a statement with an identifier that you can refer to using a break or continue statement.

with (en-US)

Extends the scope chain for a statement.

• Operators