Accessing an attribute on a child that's set with a data binding

[Rob Dodson]

I have a little bit of markup that looks like this:

<polymer-element name="blog-post" noscript>

      <template>

        

        <mark-down>

          <textarea value="{{post}}"></textarea>

        </mark-down>

        <polymer-localstorage name="my-blog-editor" value="{{post}}">

        </polymer-localstorage>

      </template>

</polymer-element>

I'd like the mark-down tag to be able to see the value of the textarea but I'm having a hard time knowing when to query for it.

Inside of mark-down my code looks something like this:

      attached: function() {

          this.textarea = this.$.textareaContent.getDistributedNodes()[0];  // this grabs the textarea element

          // create an observer instance

          var observer = new MutationObserver(function(mutations) {

            mutations.forEach(function(mutation) {

              console.log(mutation);

            });

          });

           

          // pass in the target node, as well as the observer options

          observer.observe(this.textarea, { attributes: true });

      }

Unfortunately the mutation observer never fires. I've tried checking for the value of textarea directly in attached and domReady but it's always null. The only success I've had is to use a setTimeout to check for the value asynchronously.

[Rob Dodson]

Moved to stackoverflow: http://stackoverflow.com/questions/22855083/accessing-an-attribute-on-a-child-thats-set-with-a-data-binding

[Rafael Weinstein]

i think you probably want to observe the characterData of the text-area, not the attribute.

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[Rob Dodson]

Hm, still no luck observing characterData. Here's a jsbin: http://jsbin.com/jidiyexi/2/edit

[Rafael Weinstein]

Ah, sorry. I'm not sure what I was thinking. TextArea is like input, the DOM storage values don't change when the input value changes. IOW, you can observe it's value with MutationObserver.

You need to listen to the value of the textarea.value changing. You can do that either by listening to the 'value' event or by observing the value of this.post in the blog post element.

[Scott Miles]

Fwiw, please don't fork conversations (now there some here, and some in SO).

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