JavaScript Statement & Expression
JavaScript code blocks are used to group multiple statements together.
A code block is written inside curly braces {}.
Example
javascript
{
let name = "John";
console.log(name);
}The statements inside {} belong to the same block.
A code block is a group of JavaScript statements.
Example
javascript
{
let message = "Hello JavaScript";
console.log(message);
}Here, both statements are inside one code block.
Code blocks help keep related statements together.
Code blocks are commonly used with conditions.
Example
javascript
let age = 20;
if (age >= 18) {
console.log("You are eligible.");
console.log("You can continue.");
}In this example, both console.log() statements are inside the if block.
They run only when the condition is true.
Functions also use code blocks.
Example
javascript
function showMessage() {
let message = "Welcome to JavaScript";
console.log(message);
}The code inside {} belongs to the function.
It runs when the function is called.
Example
javascript
showMessage();Loops use code blocks to repeat multiple statements.
Example
javascript
for (let i = 1; i <= 3; i++) {
console.log("Number: " + i);
}The statement inside the block runs again and again while the loop condition is true.
A code block can contain one statement or many statements.
Example
javascript
let price = 500;
let quantity = 2;
if (quantity > 0) {
let total = price * quantity;
console.log("Total Price: " + total);
}Here, the code block contains two statements.
Variables declared with let or const inside a block can be used only inside that block.
Example
javascript
{
let city = "London";
console.log(city);
}The variable city is available inside the block.
But it cannot be used outside the block.
Example
javascript
{
let city = "London";
}
console.log(city);This will not work because city was created inside the block.
The var keyword does not follow block scope in the same way as let and const.
Example
javascript
{
var country = "USA";
}
console.log(country);This can work because var is not block-scoped.
In modern JavaScript, let and const are preferred because they are safer and easier to control.
A code block can also be written inside another code block.
Example
javascript
let isLoggedIn = true;
let isAdmin = true;
if (isLoggedIn) {
console.log("User is logged in.");
if (isAdmin) {
console.log("User is an admin.");
}
}This is called a nested block.
Nested blocks are useful when one condition depends on another condition.
Complete Example
html
<!DOCTYPE html>
<html>
<head>
<title>JavaScript Code Blocks</title>
</head>
<body>
<h1>JavaScript Code Blocks</h1>
<p id="result"></p>
<script>
let userName = "John";
let age = 22;
let message = "";
if (age >= 18) {
message = userName + " is eligible.";
}
document.getElementById("result").innerHTML = message;
</script>
</body>
</html>Run the above example in the Try It Editor.
Try changing the value of age.
Also try adding more statements inside the if block.
{}.let and const inside a block are block-scoped.var do not follow block scope in the same way.JavaScript code blocks are used to group related statements together.
They are commonly used with conditions, functions, and loops.
Understanding code blocks is important because they help you write organized JavaScript code and understand how scope works.