dart2js

问题 I'm doing ZigZag encoding on 32bit integers with Dart. This is the source code that I'm using: int _encodeZigZag(int instance) => (instance << 1) ^ (instance >> 31); int _decodeZigZag(int instance) => (instance >> 1) ^ (-(instance & 1)); The code works as expected in the DartVM. But in dart2js the _decodeZigZag function is returning invalid results if I input negativ numbers. For example -10 . -10 is encoded to 19 and should be decoded back to -10 , but it is decoded to 4294967286 . If I run

问题 I'm doing ZigZag encoding on 32bit integers with Dart. This is the source code that I'm using: int _encodeZigZag(int instance) => (instance << 1) ^ (instance >> 31); int _decodeZigZag(int instance) => (instance >> 1) ^ (-(instance & 1)); The code works as expected in the DartVM. But in dart2js the _decodeZigZag function is returning invalid results if I input negativ numbers. For example -10 . -10 is encoded to 19 and should be decoded back to -10 , but it is decoded to 4294967286 . If I run

问题 I'm trying to determine if a dynamic parameter to a function is really an int or a double and I'm finding surprising behavior (at least to me). Can anyone explain this output (produced on dartpad)? foo(value) { print("$value is int: ${value is int}"); print("$value is double: ${value is double}"); print("$value runtimetype: ${value.runtimeType}"); } void main() { foo(1); foo(2.0); int x = 10; foo(x); double y = 3.1459; foo(y); double z = 2.0; foo(z); } The output: 1 is int: true 1 is double:

问题 When I create a new application using the Polymer library, it generates a sample project. The project works just fine in Dartium, but when I compile it (using pub build ), it doesn't work anymore. I get two 404's and an uncaught typeerror. Here is my console output in Chrome. GET file:///home/michael/Code/sample/build/web/packages/shadow_dom/shadow_dom.debug.js sample.html:1 GET file:///home/michael/Code/sample/build/web/packages/custom_element/custom-elements.debug.js sample.html:2 Uncaught

问题 Is there a way to check if the script is running in the dart vm or dart2js? Maybe using mirrors API? 回答1: There is no official way, as far as I know. The intent is that for all practical purposes, you shouldn't have to know if you are running native or compiled to JavaScript. That said, there are few hacks you can use. The easiest one is probably to exploit the fact that Dart has two numeric types, int and double , while JavaScript has only one, which is equivalent to Dart's double , and

问题 Unsupported operation: Can't use ownerName in reflection because it is not included in a @MirrorsUsed annotation. ownerName is just an published attribute on the polymer element. I understand there are a few things out there (on web, not on here) like this but none have a solid answer... I also get this below it: NoSuchMethodError : method not found: 'Symbol("title")' Anyone got any ideas. Been wrestling with this for 3 hours and ready to dump polymer. Though It was fun in dartium, if it

问题 dart2js probably generates .js.map , .js.deps and .precompiled.js . What's the purpose of them? and I donno why dart2js doens't remove them after finishing compile. 回答1: All files are generated by dart2js on purpose: .js : The JavaScript output of your application .precompiled.js : The JavaScript output but with content security policy (CSP) support .js.map : source map file used for debugging the JavaScript code in the browser. It contains a mapping from JavaScript to Dart code lines. .js

问题 I would like to skip some specific code on pub build. example: Log.print('something ${StackTrace.current}'); I would like that the code above was not transpilled to JS in production. 回答1: Asserts are only executed in checked mode and won't be included by pub build in production mode by default: assert(() { Log.print('something ${StackTrace.current}'); return true; }) DartPad example doesn't print it because it builds in production mode. You can also pass "environment" (not mix up with OS

问题 I'm learning Dart and its dependency manager pub and am having a tough time seeing the "forest through the trees" here. Say I want to use Polymer.dart in my project. So, in my project root, I create the following pubspec.yaml : name: test_dart description: A sample web application dependencies: browser: any polymer: ">=0.9.0 <0.10.0" I then run pub get , which goes to the pub repo and fetches the browser and polymer dependencies that I've specified. It then creates a packages directory in my

问题 Is it possible to use dart for chrome extension content scripts? The following does not seem to call anything in main() import 'dart:html'; import 'package:js/js.dart' as js; void main() { js.context.alert('Hello from Dart via JavaScript'); window.console.log("START!!!"); window.alert("alert"); } manifest.json... "content_scripts": [ { "matches": [ "http://docs.google.com/*", "https://docs.google.com/*" ], "js": [ "packages/browser/dart.js", "packages/browser/interop.js", "packages/js/dart