How to use TypeScript filter in Vue

With the continuous upgrading of front-end development technology, more and more new technologies have been introduced into our development work. Vue.js and TypeScript are undoubtedly the two most popular technologies. This article will introduce how to use TypeScript filter in Vue.js.

1. Principle of filter

The filter filter provided in Vue.js is used to format data, similar to the pipe filter in Angular. Its implementation principle is based on the built-in function Array.prototype.filter() of the JavaScript language. This function accepts a function as a parameter and returns a new array. The elements of the new array are all elements in the original array that meet the specified conditions.

In Vue.js, we can format data by defining a function as a parameter of filter. This function will receive a data that needs to be formatted.

2. How to use filter in Vue.js

There are two ways to use filter in Vue.js, one is global filter and the other is local filter .

2.1 Global filter

Global filter is defined on the Vue constructor, similar to Vue.component() and Vue.directive(), and can be used in the global scope. The code that defines the global filter is as follows:

Vue.filter('filterName', function(value) {
  // 这里实现过滤器的具体逻辑
})

At this point, we can use the filterName filter in all Vue instances.

2.2 Local filter

Local filter is defined in the Vue component and can only be used inside the component. The code to define a local filter is as follows:

export default {
  // ...
  filters: {
    filterName(value) {
      // 这里实现过滤器的具体逻辑
    }
  }
}

If we need multiple filters in our Vue component, we can define them as follows:

export default {
  // ...
  filters: {
    filter1(value) {
      // ...
    },
    filter2(value) {
      // ...
    }
  }
}

3. Used in Vue.js TypeScript defines filter

The method of using TypeScript to define filter in Vue.js is basically the same as using JavaScript to define filter, except that we need to declare the type on the parameters and return value of the function, so that it can be used during development Enjoy TypeScript's type checking and smart prompts now.

The following is a sample code that demonstrates how to use TypeScript to define a filter in Vue.js:

import Vue from 'vue';

interface IUser {
  name: string;
  age: number;
}

Vue.filter('userInfo', (value: IUser) => `${value.name}（${value.age}岁）`);

We define a global filter named userInfo, which accepts a type of IUser parameters and returns a string type.

4. Using filter

The method of using filter in the template of Vue.js is very simple. You only need to call the filter through the "|" symbol where the data is bound. Can.

For example, if we want to convert a number into currency format, we can write it like this:

<p>{{ price | currency }}</p>

price represents the data that needs to be formatted, and currency represents the global or local filter name we defined.

5. Summary

Using filters in Vue.js applications can facilitate us to format the data and display a more beautiful view. Combined with TypeScript, we can enjoy the convenience of type checking and intelligent prompts during the development process.

Of course, the premise is that we need to first understand the principle and usage of filter before we can use it more flexibly to meet our various development needs.

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