For Loop

The for loop is one of the most commonly used loops in Dart. It's perfect when you know exactly how many times you want to repeat a block of code. Think of it like doing jumping jacks - you decide upfront "I'll do 20 jumping jacks" and then count from 1 to 20.

Basic Syntax

The for loop has three main parts:

for (initialization; condition; increment/decrement) {
  // code to be executed
}

• Initialization: Set up a counter variable (usually i)
• Condition: Check if the loop should continue
• Increment/Decrement: Update the counter after each iteration

Simple Example

Let's print numbers from 1 to 5:

void main() {
  for (int i = 1; i <= 5; i++) {
    print('Number: $i');
  }
}

Output:

Number: 1
Number: 2
Number: 3
Number: 4
Number: 5

How It Works

1. int i = 1 - Initialize counter to 1
2. i <= 5 - Check if i is less than or equal to 5
3. If true, execute the code block
4. i++ - Increment i by 1
5. Repeat steps 2-4 until condition becomes false

Different Patterns

Counting Backwards

void main() {
  for (int i = 5; i >= 1; i--) {
    print('Countdown: $i');
  }
  print('Blast off! 🚀');
}

Skip Numbers (Increment by 2)

void main() {
  for (int i = 0; i <= 10; i += 2) {
    print('Even number: $i');
  }
}

Working with Lists

For loops are great for iterating through lists:

void main() {
  List<String> fruits = ['apple', 'banana', 'orange', 'grape'];
  
  for (int i = 0; i < fruits.length; i++) {
    print('Fruit ${i + 1}: ${fruits[i]}');
  }
}

Nested For Loops

You can put for loops inside other for loops to create patterns:

void main() {
  for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
      print('i = $i, j = $j');
    }
  }
}

This creates a 3x3 grid of combinations!

Common Use Cases

Use Case	Example
Counting	Print numbers 1 to 100
List processing	Calculate sum of all elements
Pattern creation	Draw shapes with asterisks
Repetitive tasks	Send emails to multiple recipients

Pro Tips

• Use meaningful variable names instead of just i when it makes sense
• Be careful with the condition to avoid infinite loops
• Remember that list indices start from 0, not 1
• You can use break to exit early or continue to skip iterations