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wxml

<!-- 数据源 -->
<view class='item-{{index}}' wx:for="{{lazyData}}" wx:key="*this.src">
  <image src='{{item.show? item.src : loadIcon}}' class='{{item.show? "active" : ""}}'></image>
  <view>a-{{index}}</view>
</view>

 

js

Page({
  data: {
    lazyData: [{
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      },
      {
        src: "https://gtd.alicdn.com/sns_logo/i7/TB1IWtgQFXXXXcmXFXXSutbFXXX.jpg_240x240xz.jpg",

      },
      {
        src: "https://gtd.alicdn.com/sns_logo/i1/TB1_f_PLXXXXXbVXpXXSutbFXXX.jpg_240x240xz.jpg",

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      },
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        src: "https://gtd.alicdn.com/sns_logo/i2/TB1cSZZNFXXXXaKaXXXSutbFXXX.jpg_240x240xz.jpg",

      },
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        src: "https://gtd.alicdn.com/sns_logo/i4/TB1MwqbLpXXXXaEXpXXSutbFXXX.jpg_240x240xz.jpg",

      },
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        src: "https://gtd.alicdn.com/sns_logo/i8/TB1RVS_QpXXXXXBXXXXSutbFXXX.jpg_240x240xz.jpg",

      },
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        src: "https://gtd.alicdn.com/sns_logo/i5/TB1xEJiLXXXXXcxaXXXSutbFXXX.jpg_240x240xz.jpg",

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        src: "https://gtd.alicdn.com/sns_logo/i6/TB1DSuHJVXXXXXmXXXXwu0bFXXX.png_240x240xz.jpg",

      },
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        src: "https://gtd.alicdn.com/sns_logo/i5/TB1aMNyLpXXXXa2XXXXSutbFXXX.jpg_240x240xz.jpg",

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        src: "https://gtd.alicdn.com/sns_logo/i8/TB1JRHEQpXXXXXwXVXXSutbFXXX.jpg_240x240xz.jpg",

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        src: "https://gtd.alicdn.com/sns_logo/i2/TB17gJ3OXXXXXcrXpXXSutbFXXX.jpg_240x240xz.jpg",

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      },
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        src: "https://gtd.alicdn.com/sns_logo/i6/TB1fVJJQFXXXXcyXpXXSutbFXXX.jpg_240x240xz.jpg",

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        src: "https://gtd.alicdn.com/sns_logo/i7/TB1IWtgQFXXXXcmXFXXSutbFXXX.jpg_240x240xz.jpg",

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        src: "https://gtd.alicdn.com/sns_logo/i1/TB1_f_PLXXXXXbVXpXXSutbFXXX.jpg_240x240xz.jpg",

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        src: "https://gtd.alicdn.com/sns_logo/i7/TB1TlOfQFXXXXX2XXXXwu0bFXXX.png_240x240xz.jpg",

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      }
    ]
  },
  onLoad: function() {
    /**
     * this - 当前对象
     * this.data.lazyData - 数据源
     * lazy_name - 数据名
     * 加载图标 - https://img.alicdn.com/tps/i3/T1QYOyXqRaXXaY1rfd-32-32.gif
     */
    lazyImg(this, this.data.lazyData, 'lazyData', 'https://img.alicdn.com/tps/i3/T1QYOyXqRaXXaY1rfd-32-32.gif')
  }
})




/**
 * 数据名必须为:lazyData或其它名(与数据以及页面相同)
 * 
 * 模拟数据：lazyData
 * 传输数据：_that,data(this,lazyData,lazy_name,loading_icon)
 */
const lazyImg = (_that, data, lazy_name, loading_icon) => {
  for (let i = 0, len = data.length; i < len; i++) {
    wx.createIntersectionObserver().relativeToViewport({
      bottom: 20
    }).observe('.item-' + i, (ret) => {
      ret.intersectionRatio > 0 ? data[i].show = true : '';
      _that.setData({
        [lazy_name]: data,
        loadIcon: loading_icon
      })
    })
  }
}

　　

 

微信官方API：wx.createIntersectionObserver ，感兴趣的可以去看看