// progress-bar.vue
<template>
 <transition name="fade">
 <div class="progress-bar" v-if="isShow">
 </div>
 </transition>
</template>

<script type="text/babel">
 export default {
 data() {
  return {
  isShow: true, // 是否顯示進度條
  val: 0, // 進度
  }
 },
 props: {
  /**
  * 每10毫秒自增幅度
  */
  step: {
  type: Number,
  default: 5,
  },
  /**
  * 初始值
  */
  initVal: {
  type: Number,
  default: 0,
  },
  /**
  * 到一定進度停止
  */
  stopVal: {
  type: Number,
  default: 80,
  },
  /**
  * 進度條繼續(xù)到成功
  */
  isOk: {
  type: Boolean,
  default: false,
  },
 },
 mounted() {
  // 初始化后加載進度，加載到百分之多少由stopVal決定
  this.val = this.initVal
  let step = this.step
  let timer = setInterval(() => {
  this.val = this.val + step
  this.$el.style.width = this.val + '%'
  // 父組件數據加載完前進度條最多到stopVal的這個百分值
  if (this.val >= this.stopVal) {
   clearInterval(timer)
   return
  }
  }, 10)
 },
 watch: {
  /**
  * 監(jiān)聽組件props變化決定是否繼續(xù)加載，一般在父組件數據加載完后改變此標志位
  */
  isOk() {
  let val = this.val
  let step = this.step
  let timer = setInterval(() => {
   val = val + step
   this.$el.style.width = val + '%'
   // 加載到百分百完成
   if (val >= 100) {
   // 關閉定時器
   clearInterval(timer)
   // 加載完成關閉進度條
   this.isShow = false
   // 加載完成的回調
   this.$emit('callback', 'load success')
   return
   }
  }, 10)
  },
 },
 }
</script>

<style lang="stylus" rel="stylesheet/stylus">
 .progress-bar {
 position fixed
 top 0
 height 6px
 width 0
 background-color #999
 }
 .fade {
 &-enter-active, &-leave-active {
  transition: all .3s
 }
 &-enter, &-leave-active {
  opacity: 0
 }
 }
</style>