JavaScript Fundamentals

If-Else Statements

Make decisions in your code - do different things based on conditions

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If-Else: Making Decisions

If-else statements let your code make choices. Like saying "IF it's raining, bring an umbrella. ELSE, wear sunglasses." Your program decides what to do based on conditions!

Like a Fork in the Road

You check a condition (question) and take different paths depending on the answer: true or false

Basic if Statement

Do something only if a condition is true

How if Works

if (condition)

{ code runs }

If the condition is true, the code inside the curly braces runs. If false, it's skipped.

Simple if Statement Example

Run code only when a condition is true

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

if-else: Two Paths

Do one thing if true, another thing if false

if-else Structure

if (condition)

{ if true }

↓

else

{ if false }

if-else Example

Take different actions based on a condition

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

else if: Multiple Conditions

Check multiple conditions in order

else if Chain

if (first condition)← Check this first

else if (second condition)← If first is false

else if (third condition)← If both false

else← If all false

Stops at First Match

JavaScript checks from top to bottom and stops as soon as one condition is true!

else if Example: Grade Calculator

Multiple conditions checked in order

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

Real-World Example: User Role Access

Different access levels based on user role

javascript

code

DarkEditable

// Check user permissions
const userRole = 'editor';

if (userRole === 'admin') {
  console.log('Full access granted');
  console.log('Can edit, delete, and manage users');
} else if (userRole === 'editor') {
  console.log('Editor access granted');
  console.log('Can create and edit content');
} else if (userRole === 'viewer') {
  console.log('Viewer access granted');
  console.log('Can only view content');
} else {
  console.log('Guest access');
  console.log('Limited features available');
}
// Output: Editor access granted
// Output: Can create and edit content

// Shipping cost calculator
const orderTotal = 75;
let shippingCost;

if (orderTotal >= 100) {
  shippingCost = 0;
  console.log('Free shipping!');
} else if (orderTotal >= 50) {
  shippingCost = 5;
  console.log('Standard shipping: $5');
} else {
  shippingCost = 10;
  console.log('Shipping: $10');
}

const finalTotal = orderTotal + shippingCost;
console.log('Total: $' + finalTotal);
// Output: Standard shipping: $5
// Output: Total: $80

Console Output

Click "Run Code" to see output here...

Common Mistakes to Avoid

Learn from these frequent errors

Using = instead of ===

if (age = 18) // ❌ Wrong! This assigns, not compares

if (age === 18) // ✅ Correct! Use === to compare

Forgetting Curly Braces

Always use { } even for single lines - it prevents bugs and makes code clearer

if (condition) {
  doSomething();  // ✅ Safe!
}

Key Takeaways

🔀

if Makes Decisions

Run code only when a condition is true

↔️

else = Otherwise

Runs when the condition is false

🔢

else if = More Options

Check multiple conditions in order

⚠️

Use === Not =

=== compares, = assigns values

Previous Topic

Ternary Operator

Concise conditional expressions using the ternary (? :) operator.

Next Topic

Switch Statements

Handling multiple conditions efficiently with switch-case statements.

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JavaScript Fundamentals

If-Else Statements

Make decisions in your code - do different things based on conditions

Find videos you like?

Save to resource drawer for future reference!

If-Else: Making Decisions

If-else statements let your code make choices. Like saying "IF it's raining, bring an umbrella. ELSE, wear sunglasses." Your program decides what to do based on conditions!

Like a Fork in the Road

You check a condition (question) and take different paths depending on the answer: true or false

Basic if Statement

Do something only if a condition is true

How if Works

if (condition)

{ code runs }

If the condition is true, the code inside the curly braces runs. If false, it's skipped.

Simple if Statement Example

Run code only when a condition is true

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

if-else: Two Paths

Do one thing if true, another thing if false

if-else Structure

if (condition)

{ if true }

↓

else

{ if false }

if-else Example

Take different actions based on a condition

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

else if: Multiple Conditions

Check multiple conditions in order

else if Chain

if (first condition)← Check this first

else if (second condition)← If first is false

else if (third condition)← If both false

else← If all false

Stops at First Match

JavaScript checks from top to bottom and stops as soon as one condition is true!

else if Example: Grade Calculator

Multiple conditions checked in order

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

Real-World Example: User Role Access

Different access levels based on user role

javascript

code

DarkEditable

// Check user permissions
const userRole = 'editor';

// Shipping cost calculator
const orderTotal = 75;
let shippingCost;

const finalTotal = orderTotal + shippingCost;
console.log('Total: $' + finalTotal);
// Output: Standard shipping: $5
// Output: Total: $80

Console Output

Click "Run Code" to see output here...

Common Mistakes to Avoid

Learn from these frequent errors

Using = instead of ===

if (age = 18) // ❌ Wrong! This assigns, not compares

if (age === 18) // ✅ Correct! Use === to compare

Forgetting Curly Braces

Always use { } even for single lines - it prevents bugs and makes code clearer

if (condition) {
  doSomething();  // ✅ Safe!
}

Key Takeaways

🔀

if Makes Decisions

Run code only when a condition is true

↔️

else = Otherwise

Runs when the condition is false

🔢

else if = More Options

Check multiple conditions in order

⚠️

Use === Not =

=== compares, = assigns values

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Ternary Operator

Switch Statements

JavaScript Code Editor

Building Your Learning Module...

If-Else Statements

If-Else: Making Decisions

Like a Fork in the Road

How if Works

Simple if Statement Example

if-else Structure

if-else Example

else if Chain

Stops at First Match

else if Example: Grade Calculator

Real-World Example: User Role Access

Using = instead of ===

Forgetting Curly Braces

Key Takeaways

if Makes Decisions

else = Otherwise

else if = More Options

Use === Not =

Ternary Operator

Switch Statements

JavaScript Code Editor

If-Else Statements

If-Else: Making Decisions

Like a Fork in the Road

How if Works

Simple if Statement Example

if-else Structure

if-else Example

else if Chain

Stops at First Match

else if Example: Grade Calculator

Real-World Example: User Role Access

Using = instead of ===

Forgetting Curly Braces

Key Takeaways

if Makes Decisions

else = Otherwise

else if = More Options

Use === Not =