Add JSNative utility class with static methods methods to efficiently manipulate typed JSInterop ob…

sdk/lib/js_util/dart2js/js_util_dart2js.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Utility methods to efficiently manipulate typed JSInterop objects in cases
+/// where the name to call is not known at runtime. You should only use these
+/// methods when the same effect cannot be achieved with @JS annotations.
+/// These methods would be extension methods on JSObject if Dart supported
+/// extension methods.
+library dart.js_util;
+
+import 'dart:_foreign_helper' show JS;
+import 'dart:collection' show HashMap;
+
+/// WARNING: performance of this method is much worse than other uitil
+/// methods in this library. Only use this method as a last resort.
+///
+/// Recursively converts a JSON-like collection of Dart objects to a
+/// collection of JavaScript objects and returns a [JsObject] proxy to it.
+///
+/// [object] must be a [Map] or [Iterable], the contents of which are also
+/// converted. Maps and Iterables are copied to a new JavaScript object.
+/// Primitives and other transferrable values are directly converted to their
+/// JavaScript type, and all other objects are proxied.
+jsify(object) {
+  if ((object is! Map) && (object is! Iterable)) {
+    throw new ArgumentError("object must be a Map or Iterable");
+  }
+  return _convertDataTree(object);
+}
+
+_convertDataTree(data) {
+  var _convertedObjects = new HashMap.identity();
+
+  _convert(o) {
+    if (_convertedObjects.containsKey(o)) {
+      return _convertedObjects[o];
+    }
+    if (o is Map) {
+      final convertedMap = JS('=Object', '{}');
+      _convertedObjects[o] = convertedMap;
+      for (var key in o.keys) {
+        JS('=Object', '#[#]=#', convertedMap, key, _convert(o[key]));
+      }
+      return convertedMap;
+    } else if (o is Iterable) {
+      var convertedList = [];
+      _convertedObjects[o] = convertedList;
+      convertedList.addAll(o.map(_convert));
+      return convertedList;
+    } else {
+      return o;
+    }
+  }
+
+  return _convert(data);
+}
+
+JSObject newObject() => JS('=Object', '{}');
+
+hasProperty(o, name) => JS('bool', '# in #', name, o);
+getProperty(o, name) => JS('Object', '#[#]', o, name);
+setProperty(o, name, value) => JS('', '#[#]=#', o, name, value);
+
+callMethod(o, String method, List args) =>
+    JS('Object', '#[#].apply(#, #)', o, method, o, args);
+
+instanceof(o, Function type) => JS('bool', '# instanceof #', o, type);
+callConstructor(Function constr, List arguments) {
+  if (arguments == null) {
+    return JS('Object', 'new #()', constr);
+  }
+
+  if (JS('bool', '# instanceof Array', arguments)) {
+    int argumentCount = JS('int', '#.length', arguments);
+    switch (argumentCount) {
+      case 0:
+        return JS('Object', 'new #()', constr);
+
+      case 1:
+        var arg0 = JS('', '#[0]', arguments);
+        return JS('Object', 'new #(#)', constr, arg0);
+
+      case 2:
+        var arg0 = JS('', '#[0]', arguments);
+        var arg1 = JS('', '#[1]', arguments);
+        return JS('Object', 'new #(#, #)', constr, arg0, arg1);
+
+      case 3:
+        var arg0 = JS('', '#[0]', arguments);
+        var arg1 = JS('', '#[1]', arguments);
+        var arg2 = JS('', '#[2]', arguments);
+        return JS('Object', 'new #(#, #, #)', constr, arg0, arg1, arg2);
+
+      case 4:
+        var arg0 = JS('', '#[0]', arguments);
+        var arg1 = JS('', '#[1]', arguments);
+        var arg2 = JS('', '#[2]', arguments);
+        var arg3 = JS('', '#[3]', arguments);
+        return JS(
+            'Object', 'new #(#, #, #, #)', constr, arg0, arg1, arg2, arg3);
+    }
+  }
+
+  // The following code solves the problem of invoking a JavaScript
+  // constructor with an unknown number arguments.
+  // First bind the constructor to the argument list using bind.apply().
+  // The first argument to bind() is the binding of 't', so add 'null' to
+  // the arguments list passed to apply().
+  // After that, use the JavaScript 'new' operator which overrides any binding
+  // of 'this' with the new instance.
+  var args = [null]..addAll(arguments);
+  var factoryFunction = JS('', '#.bind.apply(#, #)', constr, constr, args);
+  // Without this line, calling factoryFunction as a constructor throws
+  JS('String', 'String(#)', factoryFunction);
+  // This could return an UnknownJavaScriptObject, or a native
+  // object for which there is an interceptor
+  return JS('Object', 'new #()', factoryFunction);
+
+  // TODO(sra): Investigate:
+  //
+  //     var jsObj = JS('', 'Object.create(#.prototype)', constr);
+  //     JS('', '#.apply(#, #)', constr, jsObj,
+  //         []..addAll(arguments.map(_convertToJS)));
+  //     return _wrapToDart(jsObj);
+}