🔁 Mastering for
Loops in Dart – A Complete Beginner’s Guide
💡 Introduction
When you need to repeat a task multiple times, instead of writing the same code again and again, you use a loop. Among the loops available in Dart (for
, while
, do-while
, and for-in
), the for
loop is the most common and powerful.
Think of a for
loop like a teacher taking attendance: she starts at roll number 1 and continues until all students are checked.
📋 Keywords
-
for
-
break
-
continue
-
i++
(increment)
-
i--
(decrement)
for
break
continue
i++
(increment)
i--
(decrement)
🧠 Understanding the for
Loop
🔁 Syntax:
for (initialization; condition; increment/decrement) { // body of loop}
// body of loop}
🧱 Parts Explained:
-
Initialization: Runs once at the beginning (e.g., int i = 0
)
-
Condition: Checked before every loop run (e.g., i < 5
)
-
Increment/Decrement: Runs after each loop iteration (i++
, i--
, etc.)
Initialization: Runs once at the beginning (e.g., int i = 0
)
Condition: Checked before every loop run (e.g., i < 5
)
Increment/Decrement: Runs after each loop iteration (i++
, i--
, etc.)
✅ Basic Example:
void main() { for (int i = 1; i <= 5; i++) { print('Hello $i'); }}
for (int i = 1; i <= 5; i++) { print('Hello $i'); }}
Output:
Hello 1
Hello 2Hello 3Hello 4Hello 5
🔧 Variations of for
Loop
1. Countdown Loop
void main() { for (int i = 5; i >= 1; i--) { print('Countdown: $i'); }}
for (int i = 5; i >= 1; i--) { print('Countdown: $i'); }}
2. Loop with Step Size (e.g., print even numbers)
void main() { for (int i = 2; i <= 10; i += 2) { print(i); }}
for (int i = 2; i <= 10; i += 2) { print(i); }}
3. Loop with break
Stops the loop early.
void main() {
for (int i = 1; i <= 10; i++) {if (i == 6) break;print(i);}}
Output:
1 2 3 4 5
4. Loop with continue
Skips current iteration.
void main() {
for (int i = 1; i <= 5; i++) {if (i == 3) continue;print(i);}}
Output:
1 2 4 5
5. Nested for
Loops (Pattern Printing)
void main() { for (int i = 1; i <= 3; i++) { for (int j = 1; j <= i; j++) { stdout.write('*'); } print(''); }}
for (int i = 1; i <= 3; i++) { for (int j = 1; j <= i; j++) { stdout.write('*'); } print(''); }}
Output:
*
*****
✅ Solved Examples
1. Sum of first 10 numbers
void main() { int sum = 0; for (int i = 1; i <= 10; i++) { sum += i; } print('Sum = $sum');}
int sum = 0; for (int i = 1; i <= 10; i++) { sum += i; } print('Sum = $sum');}
2. Multiplication Table of 7
void main() { for (int i = 1; i <= 10; i++) { print('7 x $i = ${7 * i}'); }}
for (int i = 1; i <= 10; i++) { print('7 x $i = ${7 * i}'); }}
3. Reverse String
void main() { String text = 'dart'; String reverse = ''; for (int i = text.length - 1; i >= 0; i--) { reverse += text[i]; } print('Reversed: $reverse');}
String text = 'dart'; String reverse = ''; for (int i = text.length - 1; i >= 0; i--) { reverse += text[i]; } print('Reversed: $reverse');}
❓ Unsolved Practice Problems
You can try solving these using a for
loop in DartPad or your local IDE.
You can try solving these using a for
loop in DartPad or your local IDE.
1. Print numbers from 1 to 50
2. Print all odd numbers between 1 to 100
3. Print squares of numbers from 1 to 10
4. Print a triangle pattern of #
like:
##########
#########
5. Calculate factorial of a number (e.g., 5! = 120)
6. Find the sum of all even numbers from 1 to 100
7. Count digits in a given number (e.g., 51293 → 5 digits)
🧾 Summary
Feature | Description |
---|---|
for loop |
Repeats code using counter logic |
break |
Stops loop early |
continue |
Skips current round, goes to next |
i++ , i-- |
Common ways to step through the loop |
Nested loops | Used for grids or patterns |
🔚 Conclusion
The for
loop is your best friend when repeating tasks in Dart. Whether it’s printing a series, summing numbers, or building patterns, for
is fast, clean, and easy to use.
Would you like a downloadable PDF with diagrams, MCQs, and fill-in-the-blanks for your students? Or should I format this as an HTML blog post with colors and cards?