Learn Dart - 10 Code Examples & CST Typing Practice Test

Dart is a modern, object-oriented programming language developed by Google, optimized for building web, server, and mobile applications, particularly for Flutter. It emphasizes performance, strong typing, and productive development.

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Dart Theme Toggle and Counter Dart Counter with History Dart Counter with Conditional Theme Dart Counter with Lambda Actions Dart Counter with Max Limit Dart Counter with Timer Auto-Increment Dart Counter with User Input Dart Counter with Event Callbacks Dart Counter with Custom Step Dart Counter with Persistent Storage

Learn DART with Real Code Examples

Updated Nov 21, 2025

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Code Sample Descriptions

Dart Theme Toggle and Counter

void main() {
    int count = 0;
    bool isDark = false;

    void updateUI() {
        print('Counter: $count');
        print('Theme: ${isDark ? 'Dark' : 'Light'}');
    }

    void increment() { count++; updateUI(); }
    void decrement() { count--; updateUI(); }
    void reset() { count = 0; updateUI(); }
    void toggleTheme() { isDark = !isDark; updateUI(); }

    updateUI();
    increment();
    increment();
    toggleTheme();
    decrement();
    reset();
}

Demonstrates a simple counter with theme toggling in Dart, runnable in console or Flutter environment.

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Dart Counter with History

void main() {
    int count = 0;
    List<String> history = [];

    void updateUI() {
        print('Counter: $count');
        print('History: ${history.join(', ')}');
    }

    void increment() {
        count++;
        history.add('Incremented to $count');
        updateUI();
    }

    void decrement() {
        count--;
        history.add('Decremented to $count');
        updateUI();
    }

    void reset() {
        count = 0;
        history.clear();
        history.add('Counter reset');
        updateUI();
    }

    updateUI();
    increment();
    increment();
    decrement();
    reset();
}

A console-based counter that logs each increment/decrement action in a history list.

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Dart Counter with Conditional Theme

void main() {
    int count = 0;
    bool isDark = false;

    void updateUI() {
        isDark = count % 2 == 0;
        print('Counter: $count');
        print('Theme: ${isDark ? 'Dark' : 'Light'}');
    }

    void increment() { count++; updateUI(); }
    void decrement() { count--; updateUI(); }
    void reset() { count = 0; updateUI(); }

    updateUI();
    increment();
    increment();
    increment();
    decrement();
    reset();
}

Counter that switches theme based on value thresholds in Dart console app.

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Dart Counter with Lambda Actions

void main() {
    int count = 0;
    bool isDark = false;

    var updateUI = () => print('Counter: $count, Theme: ${isDark ? 'Dark' : 'Light'}');
    var increment = () { count++; updateUI(); };
    var decrement = () { count--; updateUI(); };
    var reset = () { count = 0; updateUI(); };
    var toggleTheme = () { isDark = !isDark; updateUI(); };

    updateUI();
    increment();
    toggleTheme();
    decrement();
    reset();
}

Demonstrates using Dart anonymous functions (lambdas) for counter actions and theme toggling.

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Dart Counter with Max Limit

void main() {
    int count = 0;
    int maxLimit = 5;

    void updateUI() => print('Counter: $count');

    void increment() {
        if(count < maxLimit) count++;
        updateUI();
    }

    void decrement() { count--; updateUI(); }
    void reset() { count = 0; updateUI(); }

    updateUI();
    increment();
    increment();
    increment();
    increment();
    increment();
    increment(); // won't exceed maxLimit
    reset();
}

A counter that stops incrementing after reaching a maximum limit.

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Dart Counter with Timer Auto-Increment

import 'dart:async';

void main() {
    int count = 0;

    Timer.periodic(Duration(seconds: 1), (timer) {
        count++;
        print('Counter: $count');
        if(count >= 5) timer.cancel();
    });
}

Automatically increments the counter every second using Dart Timer.

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Dart Counter with User Input

import 'dart:io';

void main() {
    int count = 0;
    while(true) {
        print('Counter: $count');
        stdout.write('Enter i/d/r/q: ');
        String? input = stdin.readLineSync();
        if(input == 'i') count++;
        else if(input == 'd') count--;
        else if(input == 'r') count = 0;
        else if(input == 'q') break;
    }
}

A console-based counter that takes user input to increment, decrement, or reset.

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Dart Counter with Event Callbacks

void main() {
    int count = 0;

    void onUpdate(int value) => print('Counter: $value');

    void increment(void Function(int) callback) {
        count++;
        callback(count);
    }

    void decrement(void Function(int) callback) {
        count--;
        callback(count);
    }

    void reset(void Function(int) callback) {
        count = 0;
        callback(count);
    }

    increment(onUpdate);
    increment(onUpdate);
    decrement(onUpdate);
    reset(onUpdate);
}

Uses callback functions to handle increment, decrement, and reset events.

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Dart Counter with Custom Step

void main() {
    int count = 0;
    int step = 3;

    void updateUI() => print('Counter: $count');

    void increment() { count += step; updateUI(); }
    void decrement() { count -= step; updateUI(); }
    void reset() { count = 0; updateUI(); }

    updateUI();
    increment();
    decrement();
    reset();
}

A counter that can increment or decrement by a custom step value.

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Dart Counter with Persistent Storage

import 'dart:io';

void main() {
    File file = File('counter.txt');
    int count = 0;
    if(file.existsSync()) {
        count = int.parse(file.readAsStringSync());
    }

    void updateUI() {
        print('Counter: $count');
        file.writeAsStringSync(count.toString());
    }

    void increment() { count++; updateUI(); }
    void decrement() { count--; updateUI(); }
    void reset() { count = 0; updateUI(); }

    updateUI();
    increment();
    decrement();
    reset();
}

Stores counter value in a file to persist between program runs (console app).

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Frequently Asked Questions about Dart

What is Dart?

What are the primary use cases for Dart?

Mobile app development with Flutter. Web applications and progressive web apps (PWAs). Server-side applications with Dart VM. Command-line tools and scripts. Cross-platform desktop applications

What are the strengths of Dart?

Fast compilation and runtime performance. Seamless cross-platform development with Flutter. Strong tooling support and IDE integration. Modern syntax and developer-friendly features. Large ecosystem and package management via pub.dev

What are the limitations of Dart?

Relatively smaller ecosystem compared to JavaScript or Python. Limited support for low-level system programming. Not as widely adopted outside Flutter ecosystem. Web performance depends on JavaScript compilation. Smaller talent pool compared to more established languages

How can I practice Dart typing speed?

CodeSpeedTest offers 10+ real Dart code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

Dart Theme Toggle and Counter

void main() {
    int count = 0;
    bool isDark = false;

    void updateUI() {
        print('Counter: $count');
        print('Theme: ${isDark ? 'Dark' : 'Light'}');
    }

    void increment() { count++; updateUI(); }
    void decrement() { count--; updateUI(); }
    void reset() { count = 0; updateUI(); }
    void toggleTheme() { isDark = !isDark; updateUI(); }

    updateUI();
    increment();
    increment();
    toggleTheme();
    decrement();
    reset();
}

Demonstrates a simple counter with theme toggling in Dart, runnable in console or Flutter environment.

Let’s Try →

Dart Counter with History

void main() {
    int count = 0;
    List<String> history = [];

    void updateUI() {
        print('Counter: $count');
        print('History: ${history.join(', ')}');
    }

    void increment() {
        count++;
        history.add('Incremented to $count');
        updateUI();
    }

    void decrement() {
        count--;
        history.add('Decremented to $count');
        updateUI();
    }

    void reset() {
        count = 0;
        history.clear();
        history.add('Counter reset');
        updateUI();
    }

    updateUI();
    increment();
    increment();
    decrement();
    reset();
}

A console-based counter that logs each increment/decrement action in a history list.

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Dart Counter with Conditional Theme

void main() {
    int count = 0;
    bool isDark = false;

    void updateUI() {
        isDark = count % 2 == 0;
        print('Counter: $count');
        print('Theme: ${isDark ? 'Dark' : 'Light'}');
    }

    void increment() { count++; updateUI(); }
    void decrement() { count--; updateUI(); }
    void reset() { count = 0; updateUI(); }

    updateUI();
    increment();
    increment();
    increment();
    decrement();
    reset();
}

Counter that switches theme based on value thresholds in Dart console app.

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Dart Counter with Lambda Actions

void main() {
    int count = 0;
    bool isDark = false;

    var updateUI = () => print('Counter: $count, Theme: ${isDark ? 'Dark' : 'Light'}');
    var increment = () { count++; updateUI(); };
    var decrement = () { count--; updateUI(); };
    var reset = () { count = 0; updateUI(); };
    var toggleTheme = () { isDark = !isDark; updateUI(); };

    updateUI();
    increment();
    toggleTheme();
    decrement();
    reset();
}

Demonstrates using Dart anonymous functions (lambdas) for counter actions and theme toggling.

Let’s Try →

Dart Counter with Max Limit

void main() {
    int count = 0;
    int maxLimit = 5;

    void updateUI() => print('Counter: $count');

    void increment() {
        if(count < maxLimit) count++;
        updateUI();
    }

    void decrement() { count--; updateUI(); }
    void reset() { count = 0; updateUI(); }

    updateUI();
    increment();
    increment();
    increment();
    increment();
    increment();
    increment(); // won't exceed maxLimit
    reset();
}

A counter that stops incrementing after reaching a maximum limit.

Let’s Try →

Dart Counter with Timer Auto-Increment

import 'dart:async';

void main() {
    int count = 0;

    Timer.periodic(Duration(seconds: 1), (timer) {
        count++;
        print('Counter: $count');
        if(count >= 5) timer.cancel();
    });
}

Automatically increments the counter every second using Dart Timer.

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Dart Counter with User Input

import 'dart:io';

void main() {
    int count = 0;
    while(true) {
        print('Counter: $count');
        stdout.write('Enter i/d/r/q: ');
        String? input = stdin.readLineSync();
        if(input == 'i') count++;
        else if(input == 'd') count--;
        else if(input == 'r') count = 0;
        else if(input == 'q') break;
    }
}

A console-based counter that takes user input to increment, decrement, or reset.

Let’s Try →

Dart Counter with Event Callbacks

void main() {
    int count = 0;

    void onUpdate(int value) => print('Counter: $value');

    void increment(void Function(int) callback) {
        count++;
        callback(count);
    }

    void decrement(void Function(int) callback) {
        count--;
        callback(count);
    }

    void reset(void Function(int) callback) {
        count = 0;
        callback(count);
    }

    increment(onUpdate);
    increment(onUpdate);
    decrement(onUpdate);
    reset(onUpdate);
}

Uses callback functions to handle increment, decrement, and reset events.

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Dart Counter with Custom Step

void main() {
    int count = 0;
    int step = 3;

    void updateUI() => print('Counter: $count');

    void increment() { count += step; updateUI(); }
    void decrement() { count -= step; updateUI(); }
    void reset() { count = 0; updateUI(); }

    updateUI();
    increment();
    decrement();
    reset();
}

A counter that can increment or decrement by a custom step value.

Let’s Try →

Dart Counter with Persistent Storage

import 'dart:io';

void main() {
    File file = File('counter.txt');
    int count = 0;
    if(file.existsSync()) {
        count = int.parse(file.readAsStringSync());
    }

    void updateUI() {
        print('Counter: $count');
        file.writeAsStringSync(count.toString());
    }

    void increment() { count++; updateUI(); }
    void decrement() { count--; updateUI(); }
    void reset() { count = 0; updateUI(); }

    updateUI();
    increment();
    decrement();
    reset();
}

Stores counter value in a file to persist between program runs (console app).

Let’s Try →

Frequently Asked Questions about Dart

What is Dart?

What are the primary use cases for Dart?

Mobile app development with Flutter. Web applications and progressive web apps (PWAs). Server-side applications with Dart VM. Command-line tools and scripts. Cross-platform desktop applications

What are the strengths of Dart?

What are the limitations of Dart?

How can I practice Dart typing speed?

CodeSpeedTest offers 10+ real Dart code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.