Using array notation instead of NSM on functions deeper then js.context.X

Issue

Can all objects after js.context be accessed with array notation from Dart? For example, I’d like to convert the following to use array notation:

var request = js.context.gapi.client.request(js.map(requestData));

Will the following array notation work?

var request = js.context['gapi']['client']['request'](js.map(requestData));

Also, should the following be done if trying to access JavaScript builtin methods?

js.context['JSON']['stringify'](jsonResp);

Solution

TL;DR : Starting from r24278 use array notation for properties and noSuchMethod for methods.


Using js.context['gapi']['client'] gives the same result as js.context.gapi.client. The main advantage of Array notation is that it avoids noSuchMethod. Until recently it was the only way to work around an issue in dart2js where minified does not work with noSuchMethod. This issue is fixed, and minification should work with Dart-JS interop.

I did a little benchmark some times ago :

  • For attribute access : array notation is around 10% faster than noSuchMethod. ( js.context.x vs. js.context['x'] )
  • For method access : array notation is around 50% slower than noSuchMethod. ( js.context.f() vs. js.context['f']() )

This last result is explained by 2 communications between JS and Dart for js.context['f'](). One to retrieve the function reference ( js.context['f'] ) and an other to call this function.

Last concern, using noSuchMethod can increase your dart2js result size (but not so much where I had tested it).

Answered By – Alexandre Ardhuin

Answer Checked By – Marie Seifert (FlutterFixes Admin)

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