Method createPropertyObserver

src/observer-locator.js:108–188

(obj, propertyName)

  }

  createPropertyObserver(obj, propertyName) {
    let descriptor;
    let handler;
    let xlinkResult;

    if (!(obj instanceof Object)) {
      return new PrimitiveObserver(obj, propertyName);
    }

    if (obj instanceof DOM.Element) {
      if (propertyName === 'class') {
        return new ClassObserver(obj);
      }
      if (propertyName === 'style' || propertyName === 'css') {
        return new StyleObserver(obj, propertyName);
      }
      handler = this.eventManager.getElementHandler(obj, propertyName);
      if (propertyName === 'value' && obj.tagName.toLowerCase() === 'select') {
        return new SelectValueObserver(obj, handler, this);
      }
      if (propertyName === 'checked' && obj.tagName.toLowerCase() === 'input') {
        return new CheckedObserver(obj, handler, this);
      }
      if (handler) {
        return new ValueAttributeObserver(obj, propertyName, handler);
      }
      xlinkResult = /^xlink:(.+)$/.exec(propertyName);
      if (xlinkResult) {
        return new XLinkAttributeObserver(obj, propertyName, xlinkResult[1]);
      }
      if (propertyName === 'role' && (obj instanceof DOM.Element || obj instanceof DOM.SVGElement)
        || /^\w+:|^data-|^aria-/.test(propertyName)
        || obj instanceof DOM.SVGElement && this.svgAnalyzer.isStandardSvgAttribute(obj.nodeName, propertyName)) {
        return new DataAttributeObserver(obj, propertyName);
      }
    }

    descriptor = Object.getPropertyDescriptor(obj, propertyName);

    if (hasDeclaredDependencies(descriptor)) {
      return createComputedObserver(obj, propertyName, descriptor, this);
    }

    if (descriptor) {
      const existingGetterOrSetter = descriptor.get || descriptor.set;
      if (existingGetterOrSetter) {
        if (existingGetterOrSetter.getObserver) {
          return existingGetterOrSetter.getObserver(obj);
        }

        // attempt to use an adapter before resorting to dirty checking.
        let adapterObserver = this.getAdapterObserver(obj, propertyName, descriptor);
        if (adapterObserver) {
          return adapterObserver;
        }
        return new DirtyCheckProperty(this.dirtyChecker, obj, propertyName);
      }
    }