According to the page on event handling in the docs for Vue, when you use v-on like `v-on:click="handler"` the handler function will automatically get the original DOM event as the first argument. This code snippet is directly adapted from those docs.

```js
new Vue({
  // Vue config shortened for brevity
  methods: {
    handler(event) {
      // `this` inside methods points to the Vue instance
      alert('Hello ' + this.name + '!')
      // `event` is the native DOM event
      if (event) {
        alert(event.target.tagName)
      }
    }
  }
})

```

Why the heck can I still access `event` even if I omit it from the functions parameter list like this:

```js
handler() {
  console.log(event); // Still returns the native DOM object even though
                      // I don't explicitly define `event` anywhere
}

```

Shouldn't `event` be `undefined` if I don't add it as an argument to the function?