<view class="prompt-box" hidden="{{isHidden}}">
  <view class="prompt-content contentFontColor">
    <view class="prompt-title">{{title}}</view>
    <input class="prompt-input" type="digit" bindinput="_input" value="{{cost}}" />
    <view class="prompt-btn-group">
      <button class="btn-item prompt-cancel-btn contentFontColor" bind:tap="_cancel">{{btn_cancel}}</button>
      <button class="btn-item prompt-certain-btn" bind:tap="_confirm">{{btn_certain}}</button>
    </view>
  </view>
</view>

// components/prompt/prompt.js
Component({
 options: {
  multipleSlots: true // 在组件定义时的选项中启用多slot支持
 },
 /**
  * 组件的属性列表
  */
 properties: {
  title: {      
   type: String,  
   value: '标题'  
  },
  btn_cancel: {
   type: String,
   value: '取消'
  },
  btn_certain: {
   type: String,
   value: '确定'
  }
 },
 data: {
  isHidden: true,
 },
 methods: {
  hidePrompt: function () {
   this.setData({
    isHidden: true
   })
  },
  showPrompt () {
   this.setData({
    isHidden: false
   })
  },
  /*
  * 内部私有方法建议以下划线开头
  * triggerEvent 用于触发事件
  */
  _cancel () {
    //触发cancel事件，即在外部，在组件上绑定cancel事件即可，bind:cancel，像绑定tap一样
   this.triggerEvent("cancel")
  },
  _confirm () {
   this.triggerEvent("confirm");
  },
  _input(e){
    //将参数传出去，这样在getInput函数中可以通过e去获得必要的参数
   this.triggerEvent("getInput",e.detail);   
  }
 }
})

{
 "component": true,
 "usingComponents": {}
}

/* components/vas-prompt/vas-prompt.wxss */
.prompt-box {
 position: absolute;
 left: 0;
 top: 0;
 width: 100%;
 height: 100%;
 z-index: 11;
 background: rgba(0, 0, 0, .5);
}
.prompt-content {
 position: absolute;
 left: 50%;
 top: 40%;
 width: 80%;
 max-width: 600rpx;
 border: 2rpx solid #ccc;
 border-radius: 10rpx;
 box-sizing: bordre-box;
 transform: translate(-50%, -50%); 
 overflow: hidden;
 background: #fff;
}
.prompt-title {
 width: 100%;
 padding: 20rpx;
 text-align: center;
 font-size: 40rpx;
 border-bottom: 2rpx solid gray;
}
.prompt-input{
 margin: 8%;
 padding: 10rpx 15rpx;
 width: 80%;
 height:85rpx;
 border: 1px solid #ccc;
 border-radius: 10rpx;
}
.prompt-btn-group{
 display: flex;
}
.btn-item {
 width: 35%;
 margin-bottom: 20rpx;
 height: 100rpx;
 line-height: 100rpx;
 background-color: white;
 justify-content: space-around;
}
.prompt-certain-btn{
 color: white;
 background-color: #4FEBDE;
}
.prompt-cancel-btn{
 border: 1px solid #4FEBDE;
}
.contentFontColor {
 color: #868686;
}

 "usingComponents": {
  "vas-prompt": "./components/prompt/prompt" 
 }

<prompt id="prompt" 
  title='test' 
  btn_certain='确定' 
  bind:getInput="getInput" 
  bind:cancel="cancel"
  bind:confirm="confirm">
</prompt>
<button bindtap="showPrompt">点击弹出prompt</button>

//在onReady生命周期函数中，先获取prompt实例
onReady:function(){
  this.prompt = this.selectComponent("#prompt");
},
//显示prompt
showPrompt:function(){
  this.prompt.showPrompt();
},
//将输入的value保存起来
getInput: function (e) {
  this.setData({
   value: e.detail.value
  })
},
confirm: function () {
  let _cost = this.data.value;
  if (_cost == '') {
   console.log('你还未输入');
   return;
  }
  else{
    ....
  }
 },
 cancel: function () {
  this.prompt.hidePrompt();
 },