title: Check if similar record exists in store to avoid duplicates
body: <p>I have a JsonStore with the following fields:</p>
  
  <pre><code>id
  date
  time
  type
  </code></pre>
  
  <p>I have a form that collects the three fields (<code>date</code>, <code>time</code>, <code>type</code>) and inserts a new record into the store (I save the store separately). I would like to perform a check if a record with the same combination of field values already exists in the store to avoid duplicate entries.</p>
  
  <p>I have managed to check for duplicate ID's in another store like this:</p>
  
  <pre><code>find = DepartmentMemberStore.find('member_id', value_from_form);
  if (find != -1) {
      // popup error window
      return;
  } else {
      // add new record to store
  }
  </code></pre>
  
  <p>I don't know how to check a store to see if multiple field values match.</p>