JavaScript Conditions
JavaScript if Statement
The JavaScript
ifstatement is used to run a block of code only when a condition is true.
It helps JavaScript make decisions.
Example
Example
javascript
let age = 20;
if (age >= 18) {
console.log("You are eligible.");
}In this example, the code inside the if block runs only when age is greater than or equal to 18.
What is an if Statement?
An if statement checks a condition.
If the condition is true, JavaScript runs the code inside the curly braces {}.
If the condition is false, JavaScript skips that code.
Syntax
Syntax
javascript
if (condition) {
// code runs when condition is true
}The condition is written inside parentheses ().
The code block is written inside curly braces {}.
Simple if Statement Example
Example
javascript
let marks = 75;
if (marks >= 40) {
console.log("You passed the exam.");
}Here, the condition is:
Condition
javascript
marks >= 40Since marks is greater than 40, the message will run.
if Statement with Numbers
You can use an if statement to compare numbers.
Example
javascript
let price = 1200;
if (price > 1000) {
console.log("This product is expensive.");
}Here, the message runs only if price is greater than 1000.
if Statement with Strings
You can also compare string values.
Example
javascript
let userName = "John";
if (userName === "John") {
console.log("Hello John!");
}Here, the condition checks whether userName is exactly equal to "John".
if Statement with Boolean Values
Boolean values are commonly used with if statements.
Example
javascript
let isLoggedIn = true;
if (isLoggedIn) {
console.log("Welcome back!");
}This is the same as writing:
Example
javascript
if (isLoggedIn === true) {
console.log("Welcome back!");
}The shorter version is cleaner and commonly used.
Using Comparison Operators with if
Comparison operators are often used inside if conditions.
| Operator | Meaning |
|---|---|
<code>></code> | Greater than |
<code><</code> | Less than |
<code>>=</code> | Greater than or equal to |
<code><=</code> | Less than or equal to |
<code>==</code> | Equal value |
<code>===</code> | Equal value and equal type |
<code>!=</code> | Not equal |
<code>!==</code> | Not equal value or not equal type |
Example
javascript
let score = 90;
if (score >= 80) {
console.log("Excellent score.");
}Using Logical Operators with if
Logical operators are used when you want to check more than one condition.
Example
javascript
let age = 22;
let hasId = true;
if (age >= 18 && hasId) {
console.log("You can enter.");
}Here, both conditions must be true:
| Condition | Meaning |
|---|---|
<code>age >= 18</code> | Age must be 18 or above |
<code>hasId</code> | User must have an ID |
The && operator means AND.
Complete Example
Complete Example
html
<!DOCTYPE html>
<html>
<head>
<title>JavaScript if Statement</title>
</head>
<body>
<h1>JavaScript if Statement</h1>
<p id="result"></p>
<script>
let userName = "John";
let age = 21;
let message = "";
if (age >= 18) {
message = userName + " is eligible to vote.";
}
document.getElementById("result").innerHTML = message;
</script>
</body>
</html>Try It Yourself
Run the above example in the Try It Editor.
Try changing the value of age.
Example
javascript
let age = 16;Then check whether the message appears or not.
Important Points
- The
ifstatement is used to run code only when a condition is true. - The condition is written inside parentheses
(). - The code block is written inside curly braces
{}. - If the condition is false, the code inside the
ifblock is skipped. - Comparison operators are commonly used with
ifstatements. - Logical operators can be used to check multiple conditions.
- Use
===for strict comparison in JavaScript.
Conclusion
The JavaScript if statement is used to make decisions in code.
It checks a condition and runs a block of code only when that condition is true.
The if statement is one of the most important parts of JavaScript because it helps create dynamic and interactive programs.