Using Filters to Format Data in Vue.js

Those from Angular-land might be familiar with filters (pipes in Angular 2+). You know, those weird little expressions that have a pipe and a function after your binding value, and somehow makes it look totally different on the way out? Yeah. Well, it turns out Vue has them too! However, Vue doesn’t provide any filters out-of-the-box, so not everyone is that familiar with them.

Writing a Filter

Let’s take a look at how to implement our own boolean to string filter in Vue.js here:

<template>
  <div>
    <!-- Is it true? It's true (or It's false). -->
    <p>Is it true? {{booleanValue | boolean(`It's true`, `It's false`)}}.</p>
    <!-- Is it true? Yes (or No). -->
    <p>Is it true? {{booleanValue | boolean}}.</p>
  </div>
</template>

<script>

// The first argument is always the passed value. After that any number of arguments may be passed.
const booleanFilter = function(value, trueText, falseText) {
  return value ? trueText || 'Yes' : falseText || 'No';
}

export default {
  filters: {
    boolean: booleanFilter
  },

  data() {
    return {
      booleanValue: false
    }
  }
}
</script>

You can also use Vue.filter(name, filterFunction) to register the filter globally:

import Vue from 'vue';

const booleanFilter = function(value, trueText, falseText) {
  return value ? trueText || 'Yes' : falseText || 'No';
}

Vue.filter('boolean', booleanFilter);

...

That’s all there is to it!

It’s worth noting that filters can only be used in mustache and binding expressions ({{thing | filter}} and :prop=“thing | filter”). Unlike Angular, they can’t be used in v-if or v-for.

Community Filters

Here are a few useful community filters you might find helpful for your projects:

• vue2-filters - The standard filters from Vue 1 ported to Vue 2.
• vue-moment - Moment.js filters to format time values.
• vue-filters-kit - A few useful filters, particularly those for displaying byte and percentage values.