Method create

src/set-observation.js:30–80

(taskQueue, set)

  }

  static create(taskQueue, set) {
    let observer = new ModifySetObserver(taskQueue, set);

    let proto = setProto;
    if (proto.add !== set.add || proto.delete !== set.delete || proto.clear !== set.clear) {
      proto = {
        add: set.add,
        delete: set.delete,
        clear: set.clear
      };
    }

    set.add = function() {
      let type = 'add';
      let oldSize = set.size;
      let methodCallResult = proto.add.apply(set, arguments);
      let hasValue = set.size === oldSize;
      if (!hasValue) {
        observer.addChangeRecord({
          type: type,
          object: set,
          value: Array.from(set).pop()
        });
      }
      return methodCallResult;
    };

    set.delete = function() {
      let hasValue = set.has(arguments[0]);
      let methodCallResult = proto.delete.apply(set, arguments);
      if (hasValue) {
        observer.addChangeRecord({
          type: 'delete',
          object: set,
          value: arguments[0]
        });
      }
      return methodCallResult;
    };

    set.clear = function() {
      let methodCallResult = proto.clear.apply(set, arguments);
      observer.addChangeRecord({
        type: 'clear',
        object: set
      });
      return methodCallResult;
    };

    return observer;
  }
}