title: Clearing ExtJS combobox input field
body: <p>I have an Ext.form.ComboBox with the following properties:</p>
  
  <pre><code>fieldLabel: 'Regiune',
  valueField: 'id',
  displayField: 'reg',
  id: 'cbRegR',
  typeAhead: true,
  store: new Ext.data.JsonStore({...}),
  mode: 'local',
  emptyText: '',
  listeners:{...}
  </code></pre>
  
  <p>The problem is that I have to manually delete the combobox' input field after selecting a value from the dropdown list to view all the list items. The matter is the list displays only the items that begin with letters in input field.</p>
  
  <p>How can I clear the input field on expanding dropdown list? I tried the following but it doesn't work:</p>
  
  <pre><code>listeners: { 'expand': function() { cbRegR.clearValue(); } }
  </code></pre>
  
  <p>Seems to be easy but it ain't so for me.. Any bright ideas? Thanks in advance.</p>