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How can I log into the browser console, like console.log in JavaScript, from the Dart language?

Andreas Köberle
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  • You can also try packages like logging or scribe https://pub.dartlang.org/packages/logging https://pub.dartlang.org/packages/scribe – Hadrien Lejard Oct 31 '16 at 07:18

6 Answers6

155

Simple:

print('This will be logged to the console in the browser.');

A basic top-level print function is always available in all implementations of Dart (browser, VM, etc.). Because Dart has string interpolation, it's easy to use that to print useful stuff too:

var a = 123;
var b = Point(2, 3);
print('a is $a, b is ${b.x}, ${b.y}');
munificent
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63

Also, dart:html allows use of window.console object.

import 'dart:html';

void main() {
  window.console.debug("debug message");
  window.console.info("info message");
  window.console.error("error message");
}
nbro
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Chris Buckett
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10

It’s easy! Just import the logging package:

import 'package:logging/logging.dart';

Create a logger object: 

final _logger = Logger('YourClassName');

Then in your code when you need to log something:

_logger.info('Request received!');

If you catch an exception you can log it and the stacktrace as well.

_logger.severe('Oops, an error occurred', err, stacktrace);

Logging package documentation : https://github.com/dart-lang/logging

Lii
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Mark Madej
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    this is a dependency, needs to be added to pubspec.yml dependencies: logging: ^0.11.4 – ir2pid Feb 06 '20 at 13:08
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    You also have to add some code to make the Logger do something useful. If you only have the code above, the log messages will be sent into the void. To direct log messages to the console, for instance, you can use code like this: `// Configure logging to output to console: Logger.root.level = Level.ALL; Logger.root.onRecord.listen((record) { print('${record.level.name}: ${record.time}: ${record.message}'); });` – Pi Da Aug 05 '20 at 18:59
  • This does not answer the question of "writing to the console". Doing just what you said doest nothing unless you register a logger that writes to the console... And then you're back at square one of trying to find a way to write to the console. – Stephan Leclercq Dec 06 '20 at 07:42
5

You can use Dart's built-in log() function

import 'dart:developer';

log('data: $data');

You can also use print(), but this is not a good practice because it can slow down your program in a production environment. debugPrint, log and other methods will prevent this.

Ivan Tsaryk
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1

Simple: print("hello word"); or debugPrint(" hello word);

thanh tùng trần
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-1

When you use only Dart without Flutter, then this is a good and easy solution:

void log(var logstr) {
  stdout.writeln("-> " + logstr.toString());
}
Lars Lehmann
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