"usingComponents": {
 "van-collapse": "path/to/vant-weapp/dist/collapse/index",
 "van-collapse-item": "path/to/vant-weapp/dist/collapse-item/index"
}

<van-collapse value="{{ activeNames }}">
 <van-collapse-item title="有赞微商城" name="1">
  提供多样店铺模板，快速搭建网上商城
 </van-collapse-item>
 <van-collapse-item title="有赞零售" name="2">
  网店吸粉获客、会员分层营销、一机多种收款，告别经营低效和客户流失
 </van-collapse-item>
 <van-collapse-item title="有赞美业" name="3" disabled>
  线上拓客，随时预约，贴心顺手的开单收银
 </van-collapse-item>
</van-collapse>

Page({
 data: {
  activeNames: ['1']
 },
 onChange(event) {
  this.setData({
   activeNames: event.detail
  });
 }
});

<van-collapse :value="activeNames" @change="onChange($event)">
 <van-collapse-item title="有赞微商城" name="1">
  提供多样店铺模板，快速搭建网上商城
 </van-collapse-item>
 <van-collapse-item title="有赞零售" name="2">
  网店吸粉获客、会员分层营销、一机多种收款，告别经营低效和客户流失
 </van-collapse-item>
 <van-collapse-item title="有赞美业" name="3" disabled>
  线上拓客，随时预约，贴心顺手的开单收银
 </van-collapse-item>
</van-collapse>

export default {
 data () {
  return {
   activeName: '1'
  }
 },
 methods: {
  onChange (event) {
   console.log(event)
   this.activeName = event.mp.detail
  }
 }
}

value="{{activeNames}}"

v-bind:value="activeNames"
//或者
:value="activeNames"

@change="onChange($event)"

onChange(event){ // 获取表单组件filed的值
 console.log(event.mp.detail) // 注意加入mp
}