Utility Functions

All Polymer elements inherit from Polymer.Base, which provides a set of useful convenience functions for instances to use.

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

• toggleClass(name, bool, [node]). Toggles the named boolean class on the host element, adding the class if bool is truthy and removing it if bool is falsey. If node is specified, sets the class on node instead of the host element.

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

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

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

• fire(type, [detail], [options]). Fires a custom event. The options object can contain the following properties:

  • node. Node to fire the event on (defaults to this).

  • bubbles. Whether the event should bubble. Defaults to true.

  • cancelable. Whether the event can be canceled with preventDefault. Defaults to false.

• async(method, [wait]). 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(jobName, callback, [wait]). 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(jobName). Cancels an active debouncer without calling the callback.

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

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

• transform(transform, [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:

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

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

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

• importHref(href, onload, onerror). Dynamically imports an HTML document.

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

  Note: To call importHref from outside a Polymer element, use Polymer.Base.importHref.

• resolveUrl(url). Takes a URL relative to the <dom-module> of an imported Polymer element, and returns a path relative to the current document. This method can be used, for example, to refer to an asset delivered alongside an HTML import.