Utility Functions

All Polymer elements mix in the PolymerBase and PolymerMixin classes, which provide a set of useful convenience functions for instances to use.

• $$(String selector). Returns the first node in this element's local DOM that matches selector.

• toggleClass(String name, [bool value, Element node]). Toggles the named boolean class on the host element, adding the class if value is true and removing it if value is false or null. If node is specified, sets the class on node instead of the host element.

• toggleAttribute(String name, [bool value, Element node]). Like toggleClass, but toggles the named boolean attribute.

• attributeFollows(String name, Element newNode, Element oldNode). Moves a boolean attribute from oldNode to newNode, unsetting the attribute (if set) on oldNode and setting it on newNode.

• classFollows(String name, Element newNode, Element oldNode). Moves a class from oldNode to newNode, removing the class (if present) on oldNode and adding it to newNode.

• fire(String type, {detail, bool canBubble, bool cancelable, Node node}). Fires a custom event with the desired properties.

• int async(void callback(), {int waitTime}). Calls method asynchronously. If no wait time is specified, runs tasks with microtask timing (after the current method finishes, but before the next event from the event queue is processed). Returns a handle that can be used to cancel the task.

• cancelAsync(handle). Cancels the identified async task.

• debounce(String jobName, void callback(), {int waitTime}). Call debounce to collapse multiple requests for a named task into one invocation, which is made after the wait time has elapsed with no new request. If no wait time is given, the callback is called at microtask timing (guaranteed to be before paint).

• cancelDebouncer(String jobName). Cancels an active debouncer without calling the callback.

• flushDebouncer(String jobName). Calls the debounced callback immediately and cancels the debouncer.

• bool isDebouncerActive(String jobName). Returns true if the named debounce task is waiting to run.

• transform(String transform, [Element node]). Applies a CSS transform to the specified node, or host element if no node is specified. transform is specified as a string. For example:

   transform('rotateX(90deg)', this.$['myDiv']);
  

• translate3d(String x, String y, String z, [Element node]). Transforms the specified node, or host element if no node is specified. For example:

  this.translate3d('100px', '100px', '100px');
  

• importHref(String href, {void onLoad(e), void onError(e)}). Dynamically imports an HTML document.

  Note: To call importHref from outside a Polymer element, use Polymer.importHref. Dart Note: Html files imported this way cannot contain dart script tags.

this.importHref('path/to/page.html', (e) {
    // e.target.import is the import document.
}, (e) {
    // loading error
});