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How to add attributes to custom elements?

I am trying to add attributes in my custom elements and use it within my new element, but having a hard time with the syntax. I have seen this article , but not really clear on it's usage. How can I declare and use the custom "label" attribute in my created callback to render it?

<current-date foo="Today is: "></current-date>

<script>
  document.registerElement('current-date', {
    prototype: {
      createdCallback: function() {
        this.innerHTML = this.foo + new Date();
      },
      foo: {
        value: function() {
          alert('foo() called');
        }
      }
    }
  });
</script>

http://jsbin.com/UdOwizU/4/ (only works in Google Canary)

Maybe something like this:

<body>
  <current-date label="Today is: "></current-date>

  <script>
    document.registerElement('current-date', {
      prototype: {
        createdCallback: function() {
          this.foo = {value: function() {
            return this.attributes.getNamedItem("label").value;
          }},
          this.innerHTML = this.foo.value.call(this) + new Date();
        }
      }
    });
  </script>
</body>

http://jsbin.com/ivaWUyAL/3/edit

Maybe I get you wrong, but have you tried using setAttribute() ?

I also can't try registerElement , but it works the "usual" way:

var el = document.createElement( 'current-date' );
el.setAttribute( 'label', new Date() );
document.body.appendChild( el );

In your case this should be something like:

createdCallback: function() {
    this.innerHTML = this.foo + new Date();
    this.setAttribute( 'label', this.getAttribute( 'label' ) + new Date() );
}

您可能正在寻找的是attributeChangedCallback ,这将使您有机会在设置,删除或修改属性时运行用户代码-> http://w3c.github.io/webcomponents/spec/custom/ #类型-的-回调

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