javascript实现计算器功能详解流程

{
  "navigationBarBackgroundColor": "#fff",
  "navigationBarTextStyle": "black",
  "navigationBarTitleText": "计算器"
}

data:{
  //  data中只放置初始数据
  num:"1",
  op:" "//记录运算符号
 }

<view class="result">
    <view class="result-num">{{num}}</view>
    <view class="result-op">{{op}}</view>
</view>
<view class="btns">
  <view>
    <view hover-class="bg" bindtap="reSetBtn">C</view>
    <view hover-class="bg" bindtap="delBtn">Del</view>
    <view hover-class="bg" bindtap="opBtn" data-val="%">%</view>
    <view hover-class="bg" bindtap="opBtn" data-val="/">/</view>
  </view>
  <view>
    <view hover-class="bg" bindtap="numBtn" data-val="7">7</view>
    <view hover-class="bg" bindtap="numBtn" data-val="8">8</view>
    <view hover-class="bg" bindtap="numBtn" data-val="9">9</view>
    <view hover-class="bg" bindtap="opBtn" data-val="*">*</view>
  </view>
  <view>
    <view hover-class="bg" bindtap="numBtn" data-val="4">4</view>
    <view hover-class="bg" bindtap="numBtn" data-val="5">5</view>
    <view hover-class="bg" bindtap="numBtn" data-val="6">6</view>
    <view hover-class="bg" bindtap="opBtn" data-val="-">-</view>
  </view>
  <view>
    <view hover-class="bg" bindtap="numBtn" data-val="1">1</view>
    <view hover-class="bg" bindtap="numBtn" data-val="2">2</view>
    <view hover-class="bg" bindtap="numBtn" data-val="3">3</view>
    <view hover-class="bg" bindtap="opBtn" data-val="+">+</view>
  </view>
  <view>
    <view hover-class="bg" bindtap="numBtn" data-val="0">0</view>
    <view hover-class="bg" bindtap="doBtn" data-val=".">.</view>
    <view hover-class="bg" bindtap="opBtn" data-val="=">=</view>
  
  </view>
</view>

page{
  display: flex;
  flex-direction: column;
  height: 100%;
}
.result{
  flex: 1;
  background: #f3f6fe;
  position: relative;
}
.result-num{
  position: absolute;
  font-size: 20pt;
  bottom: 5vh;
  right: 3vw;
}
 
.result-op{
  position: absolute;
  font-size: 15pt;
  bottom: 1vh;
  right: 3vw;
}
.btns{
  flex: 1;
  display: flex;
  flex-direction: column;
  font-size: 17pt;
  border-top: 1rpx solid #ccc;
  border-left: 1rpx solid #ccc;
}
.btns>view{
  flex: 1;
  display: flex;
}
.btns>view>view{
  flex-basis: 25%;
  border-bottom: 1rpx solid #ccc;
  border-right: 1rpx solid #ccc;
  box-sizing: border-box;
  display:flex;
  align-items: center;
  justify-content: center;
}
.btns>view:last-child>view:first-child{
  flex-basis: 50%;
}
.btns>view:first-child>view:first-child{
  color:#f00;
}
.btns>view>view:last-child{
  color: #fcBe00;
}
.bg{
  background: #eee;
}

delBtn:function(e){
    var num=this.data.num.substr(0,this.data.num.length-1);
    this.setData({num:num===""? "0":num})
  }

 reSetBtn:function(e){
    //全部变成初始状态
    this.result=null;
    this.isClear=false;
    this.setData({num:"0",op:""})
  }

data:{
  //  data中只放置初始数据
  num:"1",
  op:" "//记录运算符号
 },
  result:null,
  isClear:false,//用来记录状态
  numBtn:function(e){
    var num =e.target.dataset.val//获取data-val中的值
    //如果多次按0或者isClear为true，则将原来的数据清除，显示按的数字
    if(this.data.num==='0'||this.isClear){
      this.setData({num:num})//将获取的值给result
      this.isClear=false
    }else{
        this.setData({num:this.data.num+num})
    }
  },
 
  opBtn:function(e){
    var op=this.data.op;//先记录当前的op
    var num=Number(this.data.num);//获取当前的num数据
    this.setData({op:e.target.dataset.val});//把按下的按钮给变量op
    if(this.isClear){//因为上面操作中有如果按了运算符，则isclear为true，在这里为了避免多次按加都会起作用，再return
      return
    }
    this.isClear=true;//当用户按了运算按钮，再按数字，则把原来的数字清空
    if(this.result===null){
      this.result=num;
      return
    }
    if(op==="+"){
      this.result=this.result+num
      this.setData({num:this.result})//把加出来的结果为num
    }else if(op==="-"){
      this.result=this.result-num
    }else if(op==="*"){
      this.result=this.result*num
    }else if(op==="/"){
      this.result=this.result/num
    }else if(op==="%"){
      this.result=this.result%num
    }
    this.setData({num:this.result+""})//转为字符串类型
 
  },
  doBtn:function(e){
    if(this.isClear){//表示上一个运算结束了，一开始就按.的话
      this.setData({num:"0."});
      this.isClear=false;
      return
    }
    //如果多按了.
    if(this.data.num.indexOf(".")>=0){
      return
    }
    //正常数字后面按点
    this.setData({num:this.data.num+"."})
  },