Is javascript statements are separated by colons?


Example

let x, y, z;    // Statement 1
x = 5;          // Statement 2
y = 6;          // Statement 3
z = x + y;      // Statement 4

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JavaScript Programs

A computer program is a list of "instructions" to be "executed" by a computer.

In a programming language, these programming instructions are called statements.

A JavaScript program is a list of programming statements.

In HTML, JavaScript programs are executed by the web browser.


JavaScript Statements

JavaScript statements are composed of:

Values, Operators, Expressions, Keywords, and Comments.

This statement tells the browser to write "Hello Dolly." inside an HTML element with id="demo":

Example

document.getElementById("demo").innerHTML = "Hello Dolly.";

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Most JavaScript programs contain many JavaScript statements.

The statements are executed, one by one, in the same order as they are written.

JavaScript programs (and JavaScript statements) are often called JavaScript code.


Semicolons ;

Semicolons separate JavaScript statements.

Add a semicolon at the end of each executable statement:

Examples

let a, b, c;  // Declare 3 variables
a = 5;        // Assign the value 5 to a
b = 6;        // Assign the value 6 to b
c = a + b;    // Assign the sum of a and b to c

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When separated by semicolons, multiple statements on one line are allowed:

On the web, you might see examples without semicolons.
Ending statements with semicolon is not required, but highly recommended.



JavaScript White Space

JavaScript ignores multiple spaces. You can add white space to your script to make it more readable.

The following lines are equivalent:

let person = "Hege";
let person="Hege";

A good practice is to put spaces around operators ( = + - * / ):


JavaScript Line Length and Line Breaks

For best readability, programmers often like to avoid code lines longer than 80 characters.

If a JavaScript statement does not fit on one line, the best place to break it is after an operator:


JavaScript Code Blocks

JavaScript statements can be grouped together in code blocks, inside curly brackets {...}.

The purpose of code blocks is to define statements to be executed together.

One place you will find statements grouped together in blocks, is in JavaScript functions:

Example

function myFunction() {
  document.getElementById("demo1").innerHTML = "Hello Dolly!";
  document.getElementById("demo2").innerHTML = "How are you?";
}

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In this tutorial we use 2 spaces of indentation for code blocks.
You will learn more about functions later in this tutorial.


JavaScript Keywords

JavaScript statements often start with a keyword to identify the JavaScript action to be performed.

Our Reserved Words Reference lists all JavaScript keywords.

Here is a list of some of the keywords you will learn about in this tutorial:

KeywordDescription
var Declares a variable
let Declares a block variable
const Declares a block constant
if Marks a block of statements to be executed on a condition
switch Marks a block of statements to be executed in different cases
for Marks a block of statements to be executed in a loop
function Declares a function
return Exits a function
try Implements error handling to a block of statements

JavaScript keywords are reserved words. Reserved words cannot be used as names for variables.



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.

Statements and declarations by category

For an alphabetical listing see the sidebar on the left.

Control flow

return

Specifies the value to be returned by a function.

break

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

continue

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.

throw

Throws a user-defined exception.

if...else

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

switch

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

try...catch

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

Declaring variables

var

Declares a variable, optionally initializing it to a value.

let

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

const

Declares a read-only named constant.

Functions and classes

function

Declares a function with the specified parameters.

function*

Generator Functions enable writing iterators more easily.

async function

Declares an async function with the specified parameters.

async function*

Asynchronous Generator Functions enable writing async iterators more easily.

class

Declares a class.

Iterations

do...while

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

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...in

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

for...of

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.

for await...of

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

while

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.

Others

Empty

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

Block

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

debugger

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, and other scripts.

import

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

label

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

with

Extends the scope chain for a statement.

Difference between statements and declarations

In this section, we will be mixing two kinds of constructs: statements and declarations. They are two disjoint sets of grammars. The following are declarations:

  • let
  • const
  • function
  • function*
  • async function
  • async function*
  • class
  • export (Note: it can only appear at the top-level of a module)
  • import (Note: it can only appear at the top-level of a module)

Everything else in the list above is a statement.

The terms "statement" and "declaration" have a precise meaning in the formal syntax of JavaScript that affects where they may be placed in code. For example, in most control-flow structures, the body only accepts statements — such as the two arms of an if...else:

if (condition)
  statement1;
else
  statement2;

If you use a declaration instead of a statement, it would be a SyntaxError. For example, a let declaration is not a statement, so you can't use it in its bare form as the body of an if statement.

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

On the other hand, var is a statement, so you can use it on its own as the if body.

if (condition)
  var i = 0;

You can see declarations as "binding identifiers to values", and statements as "carrying out actions". The fact that var is a statement instead of a declaration is a special case, because it doesn't follow normal lexical scoping rules and may create side effects — in the form of creating global variables, mutating existing var-defined variables, and defining variables that are visible outside of its block (because var-defined variables aren't block-scoped).

As another example, labels can only be attached to statements.

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

To get around this, you can wrap the declaration in braces — this makes it part of a block statement.

label: {
  const a = 1;
}

if (condition) {
  let i = 0;
}

Browser compatibility

BCD tables only load in the browser

See also

What are JavaScript statements separated by?

Semicolons ; Semicolons separate JavaScript statements.

What is statements in JavaScript?

Statements are used in JavaScript to control its program flow. Unlike properties, methods, and events, which are fundamentally tied to the object that owns them, statements are designed to work independently of any JavaScript object.

How many types of statements are there in JavaScript?

JavaScript supports two conditional statements: if...else and switch .

Which statement is true about JavaScript?

The correct statement about the JavaScript programming language is "It is a scripting language used to make the website interactive". 4.