How to create custom events in VueJS

by Sai gowtham2min read
How to create custom events in VueJS

Custom events helps us to communicate to parent components in Vue.js.

Let’s learn how to create custom events in vue.js with the help of exmaples.

Suppose we have a Counter component which is accepting data from its parent component with the help of props.

Counter.vue
<template>
  <div>
    <h1>Counter {{ count }}</h1>
    <button>Increment</button>
  </div>
</template>

<script>
export default {
  props: ["count"]
};
</script>

From App component we are passing data to Counter component.

App.vue
<template>
  <div>
    <Counter :count="num"/>  </div>
</template>

<script>
import Counter from "./components/Counter";
export default {
  data: function() {
    return { num: 0 };
  },
  components: {
    Counter
  }
};
</script>

The problem is currently our Increment button present in Counter component can’t do anything.

when we click on a Increment button we need to increment the num data property present inside our App component, to do that we need to create a custom event inside our Counter component.

Custom event can be created by using this syntax this.$emit('eventname').

Counter.vue
<template>
  <div>
    <h1>Counter {{ count }}</h1>
    <button @click="increment">Increment</button>
  </div>
</template>

<script>
export default {
  props: ["count"],
  methods:{
      increment:function(){
          this.$emit('handleIncrement')      }
  }
};
</script>

Now our Counter component is emitting the handleIncrement custom event to listen this event on App component we need to add @handleIncrement.

App.vue
<template>
  <div>
    <!-- listening for the custom event -->    <Counter :count="num" @handleIncrement="num++"/>  </div>
</template>

<script>
import Counter from "./components/Counter";
export default {
  data: function() {
    return { num: 0 };
  },
  components: {
    Counter
  }
};
</script>

Passing arguments

Somecases we need to increment our count value by 2 or 3 in such cases this.$emit method can also accept the value as its second argument.

Counter.vue
<template>
  <div>
    <h1>Counter {{ count }}</h1>
    <button @click="incrementBy2">Increment</button>
  </div>
</template>

<script>
export default {
  props: ["count"],
  methods:{
      incrementBy2:function(){
          this.$emit('handleIncrement',2)      }
  }
};
</script>

In parent component we can access that argument value by using $event variable.

App.vue
<template>
  <div>
    <!-- listening for the custom event with emitted value -->    <Counter :count="num" @handleIncrement="num += $event;"/>  </div>
</template>

<script>
import Counter from "./components/Counter";
export default {
  data: function() {
    return { num: 0 };
  },
  components: {
    Counter
  }
};
</script>