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| 1 Methods and annotations to specify interoperability with JavaScript APIs. |
| 2 |
| 3 *This packages requires Dart SDK 1.13.0.* |
| 4 |
| 5 *This is beta software. Please files [issues].* |
| 6 |
| 7 ### Adding the dependency |
| 8 |
| 9 Add the following to your `pubspec.yaml`: |
| 10 |
| 11 ```yaml |
| 12 dependencies: |
| 13 js: ^0.6.0 |
| 14 ``` |
| 15 |
| 16 ### Example |
| 17 |
| 18 See the [Chart.js Dart API](https://github.com/google/chartjs.dart/) for an |
| 19 end-to-end example. |
| 20 |
| 21 ### Usage |
| 22 |
| 23 #### Calling methods |
| 24 |
| 25 ```dart |
| 26 // Calls invoke JavaScript `JSON.stringify(obj)`. |
| 27 @JS("JSON.stringify") |
| 28 external String stringify(obj); |
| 29 ``` |
| 30 |
| 31 #### Classes and Namespaces |
| 32 |
| 33 ```dart |
| 34 @JS('google.maps') |
| 35 library maps; |
| 36 |
| 37 // Invokes the JavaScript getter `google.maps.map`. |
| 38 external Map get map; |
| 39 |
| 40 // `new Map` invokes JavaScript `new google.maps.Map(location)` |
| 41 @JS() |
| 42 class Map { |
| 43 external Map(Location location); |
| 44 external Location getLocation(); |
| 45 } |
| 46 |
| 47 // `new Location(...)` invokes JavaScript `new google.maps.LatLng(...)` |
| 48 // |
| 49 // We recommend against using custom JavaScript names whenever |
| 50 // possible. It is easier for users if the JavaScript names and Dart names |
| 51 // are consistent. |
| 52 @JS("LatLng") |
| 53 class Location { |
| 54 external Location(num lat, num lng); |
| 55 } |
| 56 ``` |
| 57 |
| 58 #### JavaScript object literals |
| 59 |
| 60 Many JavaScript APIs take an object literal as an argument. For example: |
| 61 ```js |
| 62 // JavaScript |
| 63 printOptions({responsive: true}); |
| 64 ``` |
| 65 |
| 66 If you want to use `printOptions` from Dart, you cannot simply pass a Dart `Map` |
| 67 object – they are are "opaque" in JavaScript. |
| 68 |
| 69 |
| 70 Instead, create a Dart class with both the `@JS()` and |
| 71 `@anonymous` annotations. |
| 72 |
| 73 ```dart |
| 74 // Dart |
| 75 void main() { |
| 76 printOptions(new Options(responsive: true)); |
| 77 } |
| 78 |
| 79 @JS() |
| 80 external printOptions(Options options); |
| 81 |
| 82 @JS() |
| 83 @anonymous |
| 84 class Options { |
| 85 external bool get responsive; |
| 86 |
| 87 external factory Options({bool responsive}); |
| 88 } |
| 89 ``` |
| 90 |
| 91 #### Passing functions to JavaScript. |
| 92 |
| 93 If you are passing a Dart function to a JavaScript API, you must wrap it using |
| 94 `allowInterop` or `allowInteropCaptureThis`. |
| 95 |
| 96 ## Contributing and Filing Bugs |
| 97 |
| 98 Please file bugs and features requests on the [Github issue tracker][issues]. |
| 99 |
| 100 We also love and accept community contributions, from API suggestions to pull re
quests. |
| 101 Please file an issue before beginning work so we can discuss the design and impl
ementation. |
| 102 We are trying to create issues for all current and future work, so if something
there intrigues you (or you need it!) join in on the discussion. |
| 103 |
| 104 Code contributors must sign the |
| 105 [Google Individual Contributor License Agreement](https://developers.google.com/
open-source/cla/individual?csw=1). |
| 106 |
| 107 [issues]: https://goo.gl/j3rzs0 |
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