title: Set selected value in a paper-menu in Polymer 1.0
body: <p>I've created a custom element which utilizes <code>paper-dropdown-menu</code> and <code>paper-menu</code> in order to manage a select box in a web form. However, when trying to set the selected value through JavaScript, even though the value updates, the element in the page does not actually show the selected item in the list afterwards.</p>
  
  <p>I've looked at countless examples and tried dozens of different methods. I wasn't sure what to use as my <code>attr-for-selected</code>, but tried <code>value</code>, <code>name</code>, and <code>label</code> so far.</p>
  
  <pre><code>&lt;dom-module is="custom-listbox"&gt;
  &lt;template&gt;
  &lt;template is="dom-repeat" items="{{dropMenus}}"&gt;
    &lt;paper-dropdown-menu id="dropdownmenu" label="Type"&gt;
      &lt;paper-menu id="menu" class="dropdown-content" selected="{{selectedValue}}" attr-for-selected="label"&gt;
      &lt;template is="dom-repeat" items="{item}}"&gt;
        &lt;paper-item{{item}}&lt;/paper-item&gt;
      &lt;/template&gt;
      &lt;/paper-menu&gt;
    &lt;/paper-dropdown-menu&gt;
  &lt;/template&gt;
  &lt;/template&gt;
  
  &lt;script&gt;
  Polymer({
    is: 'custom-listbox',
    ready: function() {
      var arr = ["value1", "value2", "value3"];
      this.set('dropMenus', [arr]);
    },
    properties: {
      selectedValue: {
        type: String,
        value: 'value1' // initially selected? ...doesn't work either.
        },
    setSelected:function(selectedVal) {
      console.log(selectedVal);
      this.selectedValue = selectedVal;
      console.log(this.selectedValue);
      }
  });
  &lt;/script&gt;
  
  &lt;/dom-module&gt;
  </code></pre>
  
  <p>Later in my app.js I try to set the selected value like so:</p>
  
  <pre><code>document.querySelector('#CustomListboxID').setSelected('value2');
  </code></pre>
  
  <p>Console logs this, showing that 'value2' was passed to the element, and that within the element, this.selectedValue was properly set to 'value2'. However, again, the element does not actually update in the page. Am I missing something?</p>
  
  <pre><code>value2
  value2
  </code></pre>
  
  <p><strong>Edit</strong></p>
  
  <p>Many of the discussions in Stack Overflow regarding this topic are tagged as <code>Polymer</code> although it isn't always indicated whether the discussion relates to version 0.5 or 1.0, which might as well be two completely different frameworks. I'm not sure if the methods I've used above are maybe outdated, for this reason...</p>
  
  <p>It seems like I should be able to use <code>paper-menu</code>'s <code>.select(value)</code> function to set the selected value like so:</p>
  
  <pre><code>this.querySelector('#menu').select(selectedVal);
  </code></pre>
  
  <p>This function is documented, and I confirmed that it exists and is being imported into paper-menu from iron-menu-behavior. However, though it throws no errors, it also does nothing.</p>