How to call function from watch?
<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>