Let's talk about how to use Filters in Vue.js

Vue.js is a popular front-end framework that has become the first choice for many developers. A great feature of Vue lets us define the behavior of controls in our own way, of which Filter is a very useful tool. This article will explain how to use Filters in Vue.js.

What are Vue.js Filters

Filters are a Vue.js feature that formats text output in templates. It can be used to convert the format of text or convert it to other formats. Filters allow us to process text in a concise way without having to perform complex operations in code.

Syntax and usage of Filters

Filters uses the pipe character (‘|’) to pipe data into the specified Filter. Filters can be used anywhere in Vue, including Vue components, directives, and Vue.js instances.

The following is the basic syntax of Filters:

{{ expression | FilterName }}

Among them, ‘expression’ is the data we want to process, and ‘FilterName’ is the Filter we defined.

For example, use the capitalize filter in Vue.js to convert the first letter of a string to uppercase:

<template>
  <div>{{ name | capitalize }}</div>
</template>

<script>
export default {
  data() {
    return {
      name: 'alice',
    };
  },
  filters: {
    capitalize: function(value) {
      if (!value) return '';
      value = value.toString();
      return value.charAt(0).toUpperCase() + value.slice(1);
    },
  },
};
</script>

In the above example, the Filters named capitalize are defined, Process the name data so that its first letter becomes uppercase.

Filters that come with Vue.js

Vue.js has many built-in Filters. The following are some commonly used built-in Filters:

1. uppercase: Convert strings to uppercase.

<template>
  <div>{{ name | uppercase }}</div>
</template>

<script>
export default {
  data() {
    return {
      name: 'alice',
    };
  },
};
</script>

2. lowercase: Convert string to lowercase.

<template>
  <div>{{ name | lowercase }}</div>
</template>

<script>
export default {
  data() {
    return {
      name: 'ALICE',
    };
  },
};
</script>

3. currency: Format a number into currency.

<template>
  <div>{{ price | currency }}</div>
</template>

<script>
export default {
  data() {
    return {
      price: 20.5,
    };
  },
};
</script>

Custom Filters

In Vue.js, we can easily customize Filters to meet our specific needs. For example, create a URL-encoded Filter that replaces spaces with plus signs.

<template>
  <div>{{ value | urlEncode }}</div>
</template>

<script>
export default {
  data() {
    return {
      value: 'Hello World',
    };
  },
  filters: {
    urlEncode: function(value) {
      return encodeURIComponent(value).replace(/%20/g, '+');
    },
  },
};
</script>

In the above code, we define a Filter named urlEncode to process the "Hello World" data and finally output it as "Hello World".

Summary

Filters are a very useful tool for Vue.js, allowing us to process output text in a concise and effective way. This article has detailed the syntax and usage of using Filters in Vue.js, as well as how to define our own Filters. By learning and using Filters, we can better master Vue.js and speed up our development.

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