this.$emit update

This code snippet is using Vue.js, a popular JavaScript framework for building user interfaces. The `$emit` method is used to emit an event from a child component to its parent component. In this case, the parent component is listening for the `update` event and will execute the corresponding code when it receives the event.

Here's an example of how you might use this code in a Vue.js component:

// Child component
this.$emit('update');

And in the parent component, you would listen for the `update` event and handle it accordingly:

// Parent component
<template>
  <div>
    <!-- Your template code here -->
  </div>
</template>

<script>
export default {
  mounted() {
    this.$on('update', () => {
      // Code to execute when the update event is received
      console.log('Update event received');
    });
  },
};
</script>