JavaScript Tutorial

JS Statements

JavaScript statements are instructions that the browser executes from top to bottom. Every action in JavaScript—like declaring variables, performing operations, or calling functions—is written as a statement.

What Are JavaScript Statements?

A JavaScript statement is a piece of code that performs an action.

Just like sentences in English end with a period, JavaScript statements usually end with a semicolon (;).

The browser reads and executes statements one by one, from top to bottom.

Example:

let x = 5;       // Statement 1
let y = 10;      // Statement 2
let z = x + y;   // Statement 3

Each line above is a separate statement.

Semicolons in JavaScript

Semicolons are used to separate JavaScript statements.

let name = "John";
let age = 25;

JavaScript can still run without semicolons in many cases, but using them is a good practice and prevents unexpected errors.

Multiple Statements on One Line

You can also write multiple statements on one line:

let a = 1; let b = 2; let c = a + b;

This is valid but not recommended for readability.

Blocks of Statements

JavaScript groups statements inside curly braces { }.
These are mostly used in functions, loops, and conditionals.

Example:

if (age >= 18) {
    console.log("You are an adult");
    alert("Welcome!");
}

The code inside { } is called a code block.

JavaScript Keywords

Some statements start with keywords, such as:

Keyword	Description
`let`	Declares a block-scoped variable
`const`	Declares a constant
`var`	Declares a function-scoped variable
`if`	Creates a condition
`for`	Creates a loop
`function`	Defines a function
`return`	Returns a value

Example:

let x = 10;
if (x > 5) {
    console.log("x is greater than 5");
}

Whitespace and Line Breaks

JavaScript ignores extra spaces and new lines, so you can format your code for better readability.

These two examples behave the same:

let x = 10 + 5;

let x =
10 +
5;

Readable code is always better.

Note: Use semicolons to avoid automatic semicolon insertion errors.

Keep statements on separate lines for readability.

Use code blocks { } to group statements inside functions or conditionals.

   <script>
      document.getElementById("elem").innerHTML = "Hello World!";
   </script>

JavaScript Statements

JavaScript programs consist of statements with appropriate syntax.
Asingle JavaScript statement may span a single or multiple lines.
JavaScript statements should be ended or be separated by semicolons ( ; ).
Below is an example of a single-line statement.

Below is an example of a single-line statement.

This statement writes the text "Hello World!" to the paragraph element with the elem id.

single-line statement Example

EXAMPLE play_arrow Run Code

<!DOCTYPE html>
<html>
<head>
   <title> Try It Yourself </title>
</head>
<body>
   <p id="elem"> First Paragraph Element </p>

   <script>
      document.getElementById("elem").innerHTML = "Hello World!";
   </script>
</body>
</html>

Explanation

In the example:

let x = 5; and let y = 7; are variable declaration statements.

The function addNumbers() block contains multiple statements grouped together.

Inside the function, let result = x + y; calculates the sum, and console.log() displays it.

Finally, addNumbers(); calls the function, which is also a statement.

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