Vue $listeners, $attrs are the handy way for passing event and data
June 29, 2020
Today, I will explain about $listeners and $attrs of Vue. These features may probably be underestimated among developers despite the handy features since there is not enough information on the internet.
Try to search $listeners vue $attrs vue. You won't grasp the whole concept of $listeners and $attrs by reading and watching the information you find. I am the one who has been feeling that way. So I decided to contribute to helping other developers who can't fully understand that.
What is $listeners? How is it used?
So, the code will be below when the click event is required. Pretty basic code of handling event. This time clickHanlder is invoked when the button is clicked. Nothing is complicated.
<button v-on:click="clickHanlder"></button>But how about this situation?
<inherited-child @click="sayHello"></inherited-child>In this situation, the click event is not invoked in inherited-child. To make it possible, click event here should be passed to inherited-child.
Adding $listeners will resolve this problem.
<inherited-child v-on="$listeners"></inherited-child>Now, sayHello function is successfully invoked when clicked. This is very straightforward. If you are a Vue developer, $listeners can be used more casually.
$listeners and v-bind="$attrs"
$listeners is used for passing the event to be invoked in a child component. As similar to $listeners, Setting v-bind="$attrs" in a parent component with props can be also used for passing data.
<inherited-child id="1" name="rei" v-bind="$attrs" @click="sayHello"></inherited-child>Both id and name props are passed to inherited-child from the parent component. And the key point is it is not necessary to receive props in the child component.
<div>
<h1>Child</h1>
<div>
$attrs -> {{$attrs.id}}, {{$attrs.name}}
</div>
</div>What kind of situation $listeners and $attrs would be useful?
I have explained about $listeners and $attrs by using an example of the parent&child components.
However, these can be more useful when you need to pass the event or data to a deeper hierarchy.
For example, In the situation below if we need to pass the event and data from A component to C component, $listeners and $attrs can be set in B component.
A component -> B component -> C component
Of course, Setting emit or props in the B component will also make it work exactly the same. However, It bothers you adding them in both B and C components.
In addition, That's not readable and also confuse the developers to update in the future. If the project has Vuex installed we could rely on storing data using that but otherwise, you could probably have an opportunity using $listeners and $attrs sometime soon.
Conclution
Vue has a lot of useful features but not all of the details are introduced carefully. Since utilizing features makes the project more concise, I will keep publishing these things to encourage especially beginners to write code more simple and clean. Thanks.