Build reusable pagination components with Vue

Paging components are very common components in web projects. Let us use Vue to build reusable paging components. For the basic structure and related event monitoring, please refer to this article.

Resource paging in Web applications is not only Great for performance, but also very useful from a user experience perspective. In this article, learn how to create a dynamic and usable pagination component using Vue.

Basic Structure

The pagination component should allow the user to access the first and last pages, move forward and backward, and switch directly to the close page.

Most applications make an API request every time the user changes a page. We need to make sure that the component allows this, but we don't want to make such a request within the component. This way, we will ensure that components are reusable throughout the application and requests are made in the operation or service layer. We can do this by triggering an event using the number of the page the user clicked on.

There are several possible ways to implement pagination on API endpoints. For this example, we assume that the API tells us the number of results for each page, the total number of pages, and the current page. These will be our dynamic props.

In contrast, if the API only tells the total number of records, then we can calculate the number of pages by dividing the number of results by the number of results per page: totalResults / resultsPerPage .

We want to render a button to the first page, previous page, page number range, next page and last page:

[first] [next] [1] [2 ] [3] [previous] [last]

For example, an effect like the picture below:

Although we hope to render a series of pages, but does not want to render all available pages. Let's allow setting a prop for the most visible buttons in our component.

Now that we know what we want the component to do and what data it requires, we can set up the HTML structure and required props.

<template id="pagination">
  <ul class="pagination">
    <li>
      <button type="button">« First</button>
    </li>
    <li>
      <button type="button">«</button>
    </li>
    <!-- 页数的范围 -->
    <li>
      <button type="button">Next »</button>
    </li>
    <li>
      <button type="button">»</button>
    </li>
  </ul>
</template>
Vue.component(&#39;pagination&#39;, {
  template: &#39;#pagination&#39;,
  props: {
    maxVisibleButtons: {
      type: Number,
      required: false,
      default: 3
    },
    totalPages: {
      type: Number,
      required: true
    },
    total: {
      type: Number,
      required: true
    },
    currentPage: {
      type: Number,
      required: true
    }
  }
})

The above code registers a pagination component. If you call this component:

<p id="app">
  <pagination></pagination>
</p>

The effect you see at this time is as follows:

Note, in order to make the component look better , adds a little style to the component.

Event Listening

Now we need to notify the parent component which button the user clicked when the user clicks the button.

We need to add an event listener for each button. The v-on directive allows listening for DOM events. In this example, I'll use the v-on shortcut to listen for click events.

In order to notify the parent node, we will use the $emit method to emit an event with a page click.

We also need to ensure that the paging button only has a current state when the page is available. In order to do this, v-bind will be used to bind the value of the disabled attribute to the current page. We still use the :v-bind shortcut key: .

To keep our template clean, we will use the computed attribute to check if the button is disabled. Using computed is also cached, which means that as long as currentPage does not change, several accesses to the same computed property will return the previously computed result without having to run the function again.

<template id="pagination">
  <ul class="pagination">
    <li>
      <button type="button" @click="onClickFirstPage" :disabled="isInFirstPage">« First</button>
    </li>
    <li>
      <button type="button" @click="onClickPreviousPage" :disabled="isInFirstPage">«</button>
    </li>
    <li v-for="page in pages">
      <button type="button" @click="onClickPage(page.name)" :disabled="page.isDisabled"> {{ page.name }}</button>
    </li>
    <li>
      <button type="button" @click="onClickNextPage" :disabled="isInLastPage">Next »</button>
    </li>
    <li>
      <button type="button" @click="onClickLastPage" :disabled="isInLastPage">»</button>
    </li>
  </ul>
</template>

Vue.component(&#39;pagination&#39;, {
  template: &#39;#pagination&#39;,
  props: {
    maxVisibleButtons: {
      type: Number,
      required: false,
      default: 3
    },
    totalPages: {
      type: Number,
      required: true
    },
    total: {
      type: Number,
      required: true
    },
    currentPage: {
      type: Number,
      required: true
    }
  },
  computed: {
    isInFirstPage: function () {
      return this.currentPage === 1
    },
    isInLastPage: function () {
      return this.currentPage === this.totalPages
    }
  },
  methods: {
    onClickFirstPage: function () {
      this.$emit(&#39;pagechanged&#39;, 1)
    },
    onClickPreviousPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.currentPage - 1)
    },
    onClickPage: function (page) {
      this.$emit(&#39;pagechanged&#39;, page)
    },
    onClickNextPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.currentPage + 1)
    },
    onClickLastPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.totalPages)
    }
  }
})

When calling the pagination component, pass totalPages and total and currentPage to the component:

<p id="app">
  <pagination :total-pages="11" :total="120" :current-page="currentPage"></pagination>
</p>

let app = new Vue({
  el: &#39;#app&#39;,
  data () {
    return {
      currentPage: 2
    }
  }
})

When you run the above code, an error will be reported:

It is not difficult to find that in pagination Among the components, we are also missing pages. From what was introduced earlier, we can easily find that we need to calculate the value of pages.

Vue.component('pagination', {
  template: '#pagination',
  props: {
    maxVisibleButtons: {
      type: Number,
      required: false,
      default: 3
    },
    totalPages: {
      type: Number,
      required: true
    },
    total: {
      type: Number,
      required: true
    },
    currentPage: {
      type: Number,
      required: true
    }
  },
  computed: {
    isInFirstPage: function () {
      return this.currentPage === 1
    },
    isInLastPage: function () {
      return this.currentPage === this.totalPages
    },
    startPage: function () {
      if (this.currentPage === 1) {
        return 1
      }
      if (this.currentPage === this.totalPages) {
        return this.totalPages - this.maxVisibleButtons + 1
      }
      return this.currentPage - 1
    },
    endPage: function () {
      return Math.min(this.startPage + this.maxVisibleButtons - 1, this.totalPages)
    },
    pages: function () {
      const range = []
      for (let i = this.startPage; i <= this.endPage; i+=1) {
        range.push({
          name: i,
          isDisabled: i === this.currentPage
        })
      }
      return range
    }
  },
  methods: {
    onClickFirstPage: function () {
      this.$emit(&#39;pagechanged&#39;, 1)
    },
    onClickPreviousPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.currentPage - 1)
    },
    onClickPage: function (page) {
      this.$emit(&#39;pagechanged&#39;, page)
    },
    onClickNextPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.currentPage + 1)
    },
    onClickLastPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.totalPages)
    }
  }
})

The result obtained at this time will no longer report an error. You will see the following effect in the browser:

Add styles

Now our component implements all the functionality we originally wanted, and Added some styling to make it look more like a pagination component rather than just a list.

We also want users to be able to clearly identify the page they are on. Let's change the color of the button representing the current page.

To do this, we can use object syntax to bind the HTML class to the current page button. When binding a class name using object syntax, Vue will automatically switch classes when the value changes.

虽然 v-for 中的每个块都可以访问父作用域范围，但是我们将使用 method 来检查页面是否处于 active 状态，以便保持我们的 templage 干净。

Vue.component('pagination', {
  template: '#pagination',
  props: {
    maxVisibleButtons: {
      type: Number,
      required: false,
      default: 3
    },
    totalPages: {
      type: Number,
      required: true
    },
    total: {
      type: Number,
      required: true
    },
    currentPage: {
      type: Number,
      required: true
    }
  },
  computed: {
    isInFirstPage: function () {
      return this.currentPage === 1
    },
    isInLastPage: function () {
      return this.currentPage === this.totalPages
    },
    startPage: function () {
      if (this.currentPage === 1) {
        return 1
      }
      if (this.currentPage === this.totalPages) {
        return this.totalPages - this.maxVisibleButtons + 1
      }
      return this.currentPage - 1
    },
    endPage: function () {
      return Math.min(this.startPage + this.maxVisibleButtons - 1, this.totalPages)
    },
    pages: function () {
      const range = []
      for (let i = this.startPage; i <= this.endPage; i+=1) {
        range.push({
          name: i,
          isDisabled: i === this.currentPage
        })
      }
      return range
    }
  },
  methods: {
    onClickFirstPage: function () {
      this.$emit(&#39;pagechanged&#39;, 1)
    },
    onClickPreviousPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.currentPage - 1)
    },
    onClickPage: function (page) {
      this.$emit(&#39;pagechanged&#39;, page)
    },
    onClickNextPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.currentPage + 1)
    },
    onClickLastPage: function () {
      this.$emit(&#39;pagechanged&#39;, this.totalPages)
    },
    isPageActive: function (page) {
      return this.currentPage === page;
    }
  }
})

接下来，在 pages 中添加当前状态：

<li v-for="page in pages">
  <button type="button" @click="onClickPage(page.name)" :disabled="page.isDisabled" :class="{active: isPageActive(page.name)}"> {{ page.name }}</button>
</li>

这个时候你看到效果如下：

 

但依然还存在一点点小问题，当你在点击别的按钮时， active 状态并不会随着切换：

 

继续添加代码改变其中的效果：

let app = new Vue({
  el: '#app',
  data () {
    return {
      currentPage: 2
    }
  },
  methods: {
    onPageChange: function (page) {
      console.log(page)
      this.currentPage = page;
    }
  }
})

在调用组件时：

<p id="app">
  <pagination :total-pages="11" :total="120" :current-page="currentPage" @pagechanged="onPageChange"></pagination>
</p>

这个时候的效果如下了：

 

到这里，基本上实现了咱想要的分页组件效果。

无障碍化处理

熟悉Bootstrap的同学都应该知道，Bootstrap中的组件都做了无障碍化的处理，就是在组件中添加了WAI-ARIA相关的设计。比如在分页按钮上添加 aria-label 相关属性：

 

在我们这个组件中，也相应的添加有关于WAI-ARIA相关的处理：

<template id="pagination">
  <ul class="pagination" aria-label="Page navigation">
    <li>
      <button type="button" @click="onClickFirstPage" :disabled="isInFirstPage" aria-label="Go to the first page">« First</button>
    </li>
    <li>
      <button type="button" @click="onClickPreviousPage" :disabled="isInFirstPage" aria-label="Previous">«</button>
    </li>
    <li v-for="page in pages">
      <button type="button" @click="onClickPage(page.name)" :disabled="page.isDisabled" :aria-label="`Go to page number ${page.name}`"> {{ page.name }}</button>
    </li>
    <li>
      <button type="button" @click="onClickNextPage" :disabled="isInLastPage" aria-label="Next">Next »</button>
    </li>
    <li>
      <button type="button" @click="onClickLastPage" :disabled="isInLastPage" aria-label="Go to the last page">»</button>
    </li>
  </ul>
</template>

这样有关于 aria 相关的属性就加上了：

 

最终的效果如下，可以点击下面的连接访问：

https://codepen.io/airen/pen/mxMLrG

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