组件化icon，来实现根据传入数据不同而显示不同图标代码。

目标：把classMap显示不同的icon功能抽象成一个组件。

分析：需要传入的参数有icon尺寸，icon种类。所以下面icon.vue里面定义了2个参数size和type，由父组件传入。
难点：css代码层叠关系这里要理清。另外vue中绑定2个class属性可以使用数组形式——：class=”[iconSize,iconType]”，如果不加数组的中括号，会导致只有第一个class类生效。

header.vue中的代码

<template>
    <icon :size="1" :type="seller.supports[0].type">icon>
    <li class="support-item" v-for="(item,index) of seller.supports" :key="index">
    <icon :size="1" :type="seller.supports[index].type" class="icon">icon>
    <span class="text">{{seller.supports[index].description}}span>
    li>
template>
<script type='text/ecmascript-6'>
import icon from '../support-icon/icon'

  components: {
    star, // ES6缩写，实际为'star': star
    icon // ES6缩写，实际为'icon': icon
  },
script>

icon.vue中的代码

<template>
  <span class="icon" :class="[iconSize,iconType]">span>
template>

<script type='text/ecmascript-6'>
export default {
  props: {
    size: { // size从父组件header里面传入，决定尺寸
      type: Number
    },
    type: { // score从父组件header里面传入，决定星星数量
      type: Number
    }
  },
  data () {
    return {
    }
  },
  created () {
    this.classMap = ['decrease', 'discount', 'special', 'invoice', 'guarantee']
  },
  components: {},

  computed: {
    iconSize () {
      return 'icon-' + this.size // 返回iconSize的值，表示不同尺寸下的icon类。使得icon类与size相关联。
    },
    iconType () {
      let result = ''
      result = this.classMap[this.type]
      return result
    }
  },

  methods: {}
}

script>
<style lang='stylus' rel='stylesheet/stylus'>
@import '../../common/stylus/mixin.styl'
.icon
  display: inline-block
  vertical-align: top
  background-repeat: no-repeat
  &.icon-1
    width: 12px
    height: 12px
    background-size: 12px 12px
    &.decrease
      bg-image('decrease_1')
    &.discount
      bg-image('discount_1')
    &.guarantee
      bg-image('guarantee_1')
    &.invoice
      bg-image('invoice_1')
    &.special
      bg-image('special_1')
  &.icon-2
    width: 16px
    height: 16px
    background-size: 16px 16px
    &.decrease
      bg-image('decrease_2')
    &.discount
      bg-image('discount_2')
    &.guarantee
      bg-image('guarantee_2')
    &.invoice
      bg-image('invoice_2')
    &.special
      bg-image('special_2')
  &.icon-3
    width: 12px
    height: 12px
    background-size: 12px 12px
    &.decrease
      bg-image('decrease_3')
    &.discount
      bg-image('discount_3')
    &.guarantee
      bg-image('guarantee_3')
    &.invoice
      bg-image('invoice_3')
    &.special
      bg-image('special_3')
  &.icon-4
    width: 16px
    height: 16px
    background-size: 16px 16px
    &.decrease
      bg-image('decrease_4')
    &.discount
      bg-image('discount_4')
    &.guarantee
      bg-image('guarantee_4')
    &.invoice
      bg-image('invoice_4')
    &.special
      bg-image('special_4')
style>

图标还是和icon.vue放一个目录就近维护。