Creating Custom Directives in VueJS

Creating Custom Directives in VueJS

In this tutorial, we are going to learn about how to create custom directives in vuejs.

What is a Directive?

Directives are custom HTML attributes prefixed with v- which tells library to do something with the dom elements.

Example: v-model,v-if,v-for (These are some built in directives).

Creating Custom Directive

Let’s create our own custom directive called v-emoji which helps us to add the emojis to our content.

Global Directives can be added before the Vue instance in main.js file.

main.js
import Vue from "vue";
import App from "./App.vue";

Vue.config.productionTip = false;

Vue.directive("emoji", {  inserted: function(el) {    el.textContent +=  '👋';  }});
new Vue({
  render: h => h(App)
}).$mount("#app");

In the above code we have created a directive called emoji where inserted is a lifecycle hook of the directive.

inserted: called when a bound element has been inserted into its parent node (this only guarantees parent node presence, not necessarily in-document).

Each hook can accept four parameters el,binding,vnode,oldvnode.

Using our custom Directive

Let’s use our custom directive inside the template.

App.vue
<template>
  <div id="app">
    <h1 v-emoji>Hello</h1>  </div>
</template>

<script>

</script>

The v-emoji directive adds the waving hand emoji to our h1 element.

output:

custom-directive-emoji

But currently v-emoji can only add waving handing emoji to our HTML elements.

Passing the values to directives

Let’s modify our emoji directive so that we can pass our own emojis to the directive instead of using the same emoji.

main.js
import Vue from "vue";
import App from "./App.vue";

Vue.config.productionTip = false;

Vue.directive("emoji", {
  inserted: function(el, binding) {
    el.textContent += " " + binding.value;  }
});

new Vue({
  render: h => h(App)
}).$mount("#app");

Now we can pass our emojis to v-emoji directive.

App.vue
<template>
  <div id="app">
    <h1 v-emoji="hand">Hello</h1>    <h1 v-emoji="smiling">Welcome to vue world</h1>  </div>
</template>

<script>
export default {
  data: function() {
    return {
      smiling: "😃",      hand: "👋"    };
  }
};
</script>

output:

passing-values-custom-directives

Adding modifiers to our custom Directives

Let’s add the border modifier to our custom directive v-emoji so that it adds border to our emoji.

main.js
import Vue from "vue";
import App from "./App.vue";

Vue.config.productionTip = false;

Vue.directive("emoji", {
  inserted: function(el, binding) {
    if (binding.modifiers.border) {      el.innerHTML += `<span style="border:1px solid #000">${        binding.value      }</span>`;    } else {
      el.textContent += " " + binding.value;
    }
  }
});

new Vue({
  render: h => h(App)
}).$mount("#app");

Using border modifier.

App.vue
<template>
  <div id="app">
    <h1 v-emoji="hand">Hello</h1>
    <h1 v-emoji.border="smiling">Welcome to vue world</h1>  </div>
</template>

<script>
export default {
  data: function() {
    return {
      smiling: "😃",
      hand: "👋"
    };
  }
};
</script>

output:

adding-modifiers-custom-directives