WeChat applet implements calculator function

<view class="content">
  <view class="xianshi">{{screenNum}}</view>
  <view class="anniu">
    <view class="item blue" bindtap="btnClick" id="{{n9}}">9</view>
    <view class="item blue" bindtap="btnClick" id="{{n8}}">8</view>
    <view class="item blue" bindtap="btnClick" id="{{n7}}">7</view>
    <view class="item blue" bindtap="btnClick" id="{{na}}">+</view>
  </view>
   <view class="anniu">
    <view class="item blue" bindtap="btnClick" id="{{n6}}">6</view>
    <view class="item blue" bindtap="btnClick" id="{{n5}}">5</view>
    <view class="item blue" bindtap="btnClick" id="{{n4}}">4</view>
    <view class="item blue" bindtap="btnClick" id="{{nb}}">-</view>
  </view>
   <view class="anniu">
    <view class="item blue" bindtap="btnClick" id="{{n3}}">3</view>
    <view class="item blue" bindtap="btnClick" id="{{n2}}">2</view>
    <view class="item blue" bindtap="btnClick" id="{{n1}}">1</view>
    <view class="item blue" bindtap="btnClick" id="{{nc}}">*</view>
  </view>
   <view class="anniu">
    <view class="item blue" bindtap="btnClick" id="{{n0}}">0</view>
    <view class="item blue" bindtap="btnClear">AC</view>
    <view class="item blue" bindtap="btnJs">=</view>
    <view class="item blue" bindtap="btnClick" id="{{nd}}">/</view>
  </view>
</view>

// pages/cal/cal.js
Page({
 
  /**
   * Initial data of the page */
  data: {
   n0: 0,
   n1: 1,
   n2: 2,
   n3: 3,
   n4: 4,
   n5: 5,
   n6: 6,
   n7: 7,
   n8: 8,
   n9: 9,
   na: '+',
   nb: '-',
   nc: '*',
   nd: '/',
   screenNum: 0,
   screenStr: 0,
   is_num:1
  },
 
  /**
   * Life cycle function--listen for page loading*/
  onLoad: function (options) {
  
  },
 
  /**
   * Life cycle function - listen for the completion of the initial rendering of the page*/
  onReady: function () {
  
  },
 
  /**
   * Life cycle function--monitor page display*/
  onShow: function () {
  
  },
 
  /**
   * Life cycle function--listen for page hiding*/
  onHide: function () {
  
  },
 
  /**
   * Life cycle function--monitor page uninstallation*/
  onUnload: function () {
  
  },
 
  /**
   * Page related event processing function - listen to user pull-down action */
  onPullDownRefresh: function () {
  
  },
 
  /**
   * The function that handles the bottoming event on the page*/
  onReachBottom: function () {
  
  },
 
  /**
   * User clicks on the upper right corner to share*/
  onShareAppMessage: function () {
  
  },
  btnClick:function(event){
    //console.log('The key you pressed is '+event.target.id);
    //console.log('last time' + this.data.is_num);
    var op='';
    var data=0;
    var last_is_num = this.data.is_num;
    //What is the input this timeif (event.target.id == '9' || event.target.id == '8' || event.target.id == '7' || event.target.id == '6' || event.target.id == '5' || event.target.id == '4' || event.target.id == '3' || event.target.id == '2' || event.target.id == '1' || event.target.id == '0') {
      data = event.target.id;
      this.setData({ is_num: 1 });
    }
    if (event.target.id == '+' || event.target.id == '-' || event.target.id == '*' || event.target.id == '/') {
      op = event.target.id;
      this.setData({ is_num: 0 });
    }
    if (last_is_num==1){
      //If the last time was a number if (op == ''){
        //This time it's a number if (this.data.screenNum!=0){
          this.setData({ screenNum: this.data.screenNum + data });
          this.setData({ screenStr: this.data.screenStr + data });
        }else{
          this.setData({ screenNum: data});
          this.setData({ screenStr: data });
        }
      }else{
        this.setData({ screenNum: this.data.screenNum + op });
        this.setData({ screenStr: this.data.screenStr +',' +op+',' });
      }
    }else{
      //Last time it was not a number if (data != 0) {
        //This time it's a number this.setData({ screenNum: this.data.screenNum + data });
        this.setData({ screenStr: this.data.screenStr + data });
      } else {
        return;
      }
    }
    //console.log(op+'aaaaa'+data);
    //console.log('Now is '+this.data.is_num);
    //console.log('screenNum' + this.data.screenNum);
    //console.log(this.data.screenStr);
  },
  btnJs:function(){
    console.log(this.data.screenNum);
    console.log(this.data.screenStr);
    var result=0;
    var strs = new Array(); //define an array strs = this.data.screenStr.split(","); //character segmentation for (var i = 0; i < strs.length; i++) {
      //console.log(strs[i] + i); //character output after segmentation if (strs[i]=='+'){
        result = parseInt(strs[i - 1]) + parseInt(strs[i+1]);
      }
      if (strs[i] == '-') {
        result = strs[i - 1] - strs[i + 1];
      }
      if (strs[i] == '*') {
        result = strs[i - 1] * strs[i + 1];
      }
      if (strs[i] == '/') {
        result = strs[i - 1] / strs[i + 1];
      }    
    }
    console.log('result:'+result);
    this.setData({ screenNum: result});
    this.setData({ screenStr: result });    
  },
  btnClear:function(){
    //Restore the marker to its default state this.setData({ screenNum: 0 });
    this.setData({ screenStr: 0 });
    this.setData({ is_num: 1 });      
  }
})