What are the custom functions of vue?

Vue, as one of the most popular front-end frameworks at present, has a wealth of custom functions and instructions. Among them, custom functions are a very important part of Vue. Custom functions allow developers to use their own JavaScript functions in Vue applications to handle events, computed properties, filters, and more.

In this article, we will introduce some Vue custom functions and explore their application in Vue applications. These custom functions include:

1. Custom instructions

Custom instructions are one of the most basic custom functions in Vue. They can be used to add behavior to DOM elements. Custom directives are a way to directly manipulate DOM elements and can be referenced in a component's template. For example, when the user enters data, you can use a custom directive to limit the input to numbers:

Vue.directive('numeric', {
bind: function (el, binding, vnode) {

el.addEventListener('input', function () {
  var s = el.value;
  if (s.length === 0 || isNaN(s)) {
    el.value = '';
    return;
  }
  s = parseFloat(s);
  el.value = isNaN(s) ? '' : s.toString();
});

}
});

2. Custom component

Custom component is a very common custom function in Vue. Through custom components, developers can encapsulate some common functions for easy use in multiple places. Vue's custom component is a .vue file containing template, script and style collections. For example, the following component is a counter with a button that increments the counter value each time it is clicked:

<template>
  <button @click="increment">{{ count }}</button>
</template>

<script>
  export default {
    data() {
      return {
        count: 0
      }
    },
    methods: {
      increment() {
        this.count++
      }
    }
  }
</script>

<style scoped>
button {
  background-color: blue;
  color: white;
}
</style>

3. Custom filter

Vue’s custom filter ( filters) are functions for changing the format and style of text, and they can be used for text output from any application. For example, a date formatting filter can be implemented like this:

Vue.filter('formatDate', function (value) {
var date = new Date(value);

var year = date.getFullYear();
var month = date.getMonth() 1;
var day = date.getDate();

if (month < 10) {

month = '0' + month;

}
if (day < 10) {

day = '0' + day;

}

return year '-' month '-' day;
});

4. Custom mixins

Vue mixins (mixing in) is a technology that encapsulates logical code that can be shared between multiple components. These logical codes can be common code blocks in life cycle functions, data and other components. For example, the following code shows a mixin object that adds a global event to a component:

var globalMixin = {
mounted() {

window.addEventListener('scroll', this.handleScroll)

},
destroyed() {

window.removeEventListener('scroll', this.handleScroll)

},
methods: {

handleScroll() {
  console.log('scrolling')
}

}
};

Vue.mixin(globalMixin);

Through the above examples, you can see that Vue's custom functions are very rich and diverse, and they can solve various needs we encounter in our applications. Developers can flexibly use custom functions provided by Vue according to specific needs to make applications more scalable and maintainable.

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