Analysis of custom filter function steps in Vue documents

Vue.js is a popular front-end framework that provides a range of functions and features and is very easy to get started and use. One of them is the custom filter function. This article will analyze the custom filter function steps in the Vue document.

First of all, custom filter functions in Vue are divided into global and local methods. Global filters can be used in any component in the project, local filters can only be used within a single component.

Secondly, we need to define a filter function. The filter function needs to receive one parameter, which is the data that needs to be filtered. The function must return the filtered results. For example, here is a simple custom filter function that converts a string to uppercase:

Vue.filter('uppercase', function(value) {
  return value.toUpperCase();
});

In the above example, we registered the filter function as uppercase, and Define it as a function. This function receives a parameter value, converts it to uppercase, and returns it.

Next, we need to use the filter in the Vue instance. We can use the | symbol to call this filter. For example:

<div>{{ message | uppercase }}</div>

In the above example, we use the | symbol to pass the message data into the custom filter function, and the result is an uppercase string .

In addition to using it in templates, we can also call filters in calculated properties, directives and JavaScript. For example, in the Vue instance below, we can use the uppercase filter in the computed attribute:

new Vue({
  el: '#app',
  data: {
    message: 'hello'
  },
  computed: {
    reversedMessage: function() {
      return this.message | uppercase;
    }
  },
  filters: {
    uppercase: function(value) {
      return value.toUpperCase();
    }
  }
});

In the above example, we define a computed Attribute reversedMessage, which passes message data into the uppercase filter. This filter converts the string to uppercase and back.

Finally, we need to pay attention to some details. Filter names must be globally unique. In Vue, if a filter with the same name appears, the latter will override the former. At the same time, we can also define local filters in components. Local filters only apply to this component and have no effect on other components. The way to use local filters is very simple. You only need to define a filters object inside the component and register the filter function into the object.

In summary, custom filter functions are a very useful feature in Vue. By customizing filter functions, we can format and display data according to our needs. The above is a detailed analysis of the custom filter function steps in the Vue document.

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