Dart Boolean Tutorial with Examples

Boolean
Dart Boolean vs Javascript Boolean

1. Boolean

In the Dart programming language, bool is a supported data type, which only includes 2 values, true and false.

bool is also the name of the class representing this data type.

Syntax to declare a variable of bool type:

bool myVariable1 = true;

bool myVariable2 = false;

Example:

bool_ex1.dart

void main() {
  bool value;
  value = 100 > 25;
  print(value); // true
}

Output:

true

2. Dart Boolean vs Javascript Boolean

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The Dart programming language borrows a lot of ideas from JavaScript, which is why it is so easily converted into JavaScript code. However, the bool data type in Dart and JavaScript has a few differences.

In JavaScript the values false, 0, "", null, undefined, NaN and Number.Infinite are considered false. Other values are considered true.
In Dart, only true and false are considered bool, other values cannot be converted to bool.

In JavaScript you can write code like below, which is accepted as valid:

Javascript code

var test = "abc";

if(test) {
   console.log("OK! test is true");
} else {
   console.log("Ohh no, test is false");
}

Output:

OK! test is true

However, you can't write a similar code in Dart:

Dart code (ERROR!)

void main() {
  var test = "abc";

  if (test) { // ERROR at compile time.
    print("OK! test is true");
  } else {
    print("Ohh no, test is false");
  }
}

You will get an error message from the Dart compiler:

Error compiling to JavaScript:
Warning: Interpreting this as package URI, 'package:dartpad_sample/main.dart'.
lib/main.dart:4:7:
Error: A value of type 'String' can't be assigned to a variable of type 'bool'.
  if (test) { // ERROR at compile time.
      ^
Error: Compilation failed.

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Dart Boolean Tutorial with Examples

1. Boolean

2. Dart Boolean vs Javascript Boolean

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