Detailed explanation of Vue.filter function and how to customize filters

In Vue.js, a filter (Filter) is a function that can be added in a template expression to handle text formatting and data preprocessing. The Vue.filter method is a flexible way provided by Vue.js for defining and registering global filters, which can be used in the template of any component.

1. The syntax and usage of the Vue.filter function

The syntax of the Vue.filter function is as follows:

Vue.filter( id, [definition] )

Among them, id is the name of the filter, and definition can be a function or an object. If it is a function, it will be used as a filter function; if it is an object, it can have two properties: and, which are readfunctions writeused to filter the display and filter the input, respectively.

Global filters can be defined and registered anywhere in a Vue instance using the Vue.filter function. Below is an example:

Vue.filter('capitalize', function(value) {
  if (!value) return ''
  value = value.toString()
  return value.charAt(0).toUpperCase() + value.slice(1)
})

var app = new Vue({
  el: '#app',
  data: {
    message: 'hello world'
  }
})

In the code snippet above, we defined capitalizea filter named that converts the first letter of the text to uppercase. Then, in the Vue instance, we can use that filter in the template:

<div id="app">
  <p>{
   
   { message | capitalize }}</p>
</div>

The above code will render Hello world.

Two, custom filter

In addition to defining global filters using the Vue.filter function, we can also customize local filters. In Vue components, you can use the Filters option to register local filters.

Here is an example of a custom partial filter:

<div id="app">
  <p>{
   
   { message | uppercase }}</p>
</div>

<script>
  var app = new Vue({
    el: '#app',
    data: {
      message: 'hello world'
    },
    filters: {
      uppercase: function(value) {
        if (!value) return ''
        value = value.toString()
        return value.toUpperCase()
      }
    }
  })
</script>

In the code above, we define uppercasea local filter named and use that filter in the template. Here the value will be messageconverted to uppercase and rendered.

3. Chain call of filter

In Vue.js, filters also support chained calls, that is, multiple filters can be used in one expression.

Here is an example of chaining multiple filters:

<div id="app">
  <p>{
   
   { message | capitalize | reverse }}</p>
</div>

<script>
Vue.filter('capitalize', function(value) {
  if (!value) return ''
  value = value.toString()
  return value.charAt(0).toUpperCase() + value.slice(1)
})

Vue.filter('reverse', function(value) {
  if (!value) return ''
  value = value.toString()
  return value.split('').reverse().join('')
})

var app = new Vue({
  el: '#app',
  data: {
    message: 'hello world'
  }
})
</script>

In the above code, we define two filters: capitalizefor converting the first letter of the text to uppercase, and reversefor inverting the text. Then, in the template, we used a chain call, first converting messagethe value to uppercase, then reversing and rendering it.

Summary:
This article explains in detail the syntax and usage of the Vue.filter function, and how to customize global filters and local filters. At the same time, the chain call of the filter is also introduced. By using filters reasonably, we can easily implement text formatting and data preprocessing functions, making the page more flexible and efficient. I hope it will be helpful to your Vue.js development.

Detailed explanation of Vue.filter function and how to customize filters

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