title: How to call function from watch?
body: <pre><code>data: function ()  {
      return {
         questions: []
      }
  },
  
  watch: {
      questions : function(val, oldVal) {
          foo()
      }
  },      
  
  methods: {
      foo() {
          console.log("foo called");
      }
  }
  </code></pre>
  
  <p>Produce error: <code>ReferenceError: foo is not defined</code></p>
  
  <p>Also I am looking at examples: <a href="http://vuejs-ru.github.io/vuejs.org/api/options.html#watch" rel="noreferrer">http://vuejs-ru.github.io/vuejs.org/api/options.html#watch</a></p>
  
  <p>What this string do?</p>
  
  <p><code>handler: function (val, oldVal) { /* ... */ },</code>
  <code>handler</code> it's keyword? Or it can be function? </p>