从数字渐变组件(countUp.js)谈第三方JS库的使用

1、组件封装基础
实例
父组件count-to.vue:

<template>
  <div>
    // 父组件获取DOM通过ref属性,父组件传递给子组件end-val属性
    <count-to ref="countTo" :end-val="endVal" @on-animation-end="handleEnd">
      <span slot="left">总金额： </span>
      <span slot="right">元</span>
    </count-to>
    <button @click="getNumber">获取数值</button>
    <button @click="up">更新值</button>
  </div>
</template>
<script>
import CountTo from '@/components/count-to'
export default {
  name: 'count_to',
  components: {
    CountTo
  },
  data () {
    return {
      endVal: 100
    }
  },
  methods: {
    getNumber () {
      this.$refs.countTo.getCount()
    },
    up () {
      this.endVal += Math.random() * 100
    },
    handleEnd (endVal) {
      console.log('end -> ', endVal)
    }
  }
}
</script>

子组件count-to.vue:

<template>
  <div>
    <slot name="left"></slot>
    <span ref="number" :class="countClass" :id="eleId"></span>
    <slot name="right"></slot>
  </div>
</template>
<script>
import CountUp from 'countup'
export default {
  name: 'CountTo',
  computed: {
    eleId () {
      // 当组件编译时会生成当前编译实例的id
      return `count_up_${this._uid}`
    },
    countClass () {
      return [
        'count-to-number',
        this.className
      ]
    }
  },
  data () {
    return {
      counter: {}
    }
  },
  // 接收父组件传递的参数
  props: {
    /**
     * @description 起始值
     */
    startVal: {
      type: Number,
      default: 0
    },
    /**
     * @description 最终值
     */
    endVal: {
      type: Number,
      required: true
    },
    /**
     * @description 小数点后保留几位小数
     */
    decimals: {
      type: Number,
      default: 0
    },
    /**
     * @description 动画延迟开始时间
     */
    delay: {
      type: Number,
      default: 0
    },
    /**
     * @description 渐变时长
     */
    duration: {
      type: Number,
      default: 1
    },
    /**
     * @description 是否使用变速效果
     */
    useEasing: {
      type: Boolean,
      default: false
    },
    /**
     * @description 是否使用变速效果
     */
    useGrouping: {
      type: Boolean,
      default: true
    },
    /**
     * @description 分组符号
     */
    separator: {
      type: String,
      default: ','
    },
    /**
     * @description 整数和小数分割符号
     */
    decimal: {
      type: String,
      default: '.'
    },
    className: {
      type: String,
      default: ''
    }
  },
  methods: {
    getCount () {
      return this.$refs.number.innerText
    },
    emitEndEvent () {
      setTimeout(() => {
        this.$nextTick(() => {
          // this.$emit调用父组件绑定的函数
          this.$emit('on-animation-end', Number(this.getCount()))
        })
      }, this.duration * 1000 + 5)
    }
  },
  watch: {
    endVal (newVal, oldVal) {
      this.counter.update(newVal)
      this.emitEndEvent()
    }
  },
  mounted () {
    this.$nextTick(() => {
      // 这个是实例化CountUp插件
      this.counter = new CountUp(this.eleId, this.startVal, this.endVal, this.decimals, this.duration, {
        useEasing: this.useEasing,
        useGrouping: this.useGrouping,
        separator: this.separator,
        decimal: this.decimal
      })
      setTimeout(() => {
        this.counter.start()
        this.emitEndEvent()
      }, this.delay)
    })
  }
}
</script>
<style lang="less">
@import './count-to.less';
</style>

2、组件中使用id值
从上面代码可以看出每次编译Vue组件的时候都会生成_uid标识符，并且这个_uid在相同组件的不同实例中都不一样

3、组件中获取DOM
在组件上添加ref属性,获取DOM的时候用this.$refs