用微信小程序实现计算器功能

<view class='box'>     <view class='txt'>{{screenNum}}</view>     <view capture-bind:touchstart="compute">     <view>       <button data-val='clear' class='boxtn btn1'>AC</button>       <button data-val='back' class='boxtn btn1'>←</button>       <button data-val='#' class='boxtn btn1'>#</button>       <button data-val='/' class='boxtn btn'>/</button>     </view>       <view>       <button data-val='7' class='boxtn'>7</button>       <button data-val='8' class='boxtn'>8</button>       <button data-val='9' class='boxtn'>9</button>       <button data-val='*' class='boxtn btn'>*</button>     </view>       <view>       <button data-val='4' class='boxtn'>4</button>       <button data-val='5' class='boxtn'>5</button>       <button data-val='6' class='boxtn'>6</button>       <button data-val='-' class='boxtn btn'>-</button>     </view>       <view>       <button data-val='1' class='boxtn'>1</button>       <button data-val='2' class='boxtn'>2</button>       <button data-val='3' class='boxtn'>3</button>       <button data-val='+' class='boxtn btn'>+</button>     </view>       <view>       <button data-val='1' class='boxtn btn2'>0</button>       <button data-val='.' class='boxtn'>.</button>       <button data-val='=' class='boxtn btn'>=</button>     </view>    </view></view>

.box{  width:100%;  height: 700px;  background: #000;}.txt{  color: #fff;  width: 100%;  height:120px;  font-size: 50px;  text-align: right;}.boxtn{  width: 90px;  height:90px;  display:block;  float:left;  border-radius: 50%;  line-height: 90px;  text-align: center;  margin-left: 3px;  margin-top: 5px;  color:#fff;  background: #333333;  font-weight: bold;  font-size: 25px;}.btn{  background: #f09a37;}.btn1{  background: #a5a5a5;  color:#000;}.btn2{  width: 180px;  border-radius: 40px;}

//index.js//获取应用实例const app = getApp()Page({  /**   * 页面的初始数据   */  data: {    screenNum: 0,//屏幕显示的数    currentNum: '',//当前输入的数    storage: 0,//存储的数    operator: '',//运算符    off: false,  },  compute: function (e) {    var btn_num = e.target.dataset.val;    var obj = this;    if (!isNaN(btn_num)) {      if (obj.data.off == true) {        obj.data.currentNum = ''        obj.data.off = false;      }      obj.data.currentNum += btn_num      obj.data.currentNum = Number(obj.data.currentNum);      obj.data.currentNum = obj.data.currentNum.toString();    } else {      switch (btn_num) {        case '+':        case '-':        case '*':        case '/':        case '=':          // 将当前屏幕上的数字和本次的操作符存储到变量          if (obj.data.storage == 0) {            obj.data.storage = obj.data.currentNum;            obj.data.operator = btn_num;          } else {            if (obj.data.off != true) {              if (obj.data.operator == '+') {                obj.data.currentNum = Number(obj.data.storage) + Number(obj.data.currentNum)              } else if (obj.data.operator == '-') {                obj.data.currentNum = Number(obj.data.storage) - Number(obj.data.currentNum)              } else if (obj.data.operator == '*') {                obj.data.currentNum = Number(obj.data.storage) * Number(obj.data.currentNum)              } else if (obj.data.operator == '/') {                obj.data.currentNum = Number(obj.data.storage) / Number(obj.data.currentNum)              }            }            obj.data.storage = obj.data.currentNum;            obj.data.operator = btn_num;          }          obj.data.off = true;          break;        case 'clear':          obj.data.storage = 0;          obj.data.currentNum = '0';          obj.data.operator = '';          break;        case 'back':          obj.data.currentNum = obj.data.currentNum.slice(0, -1);          if (obj.data.currentNum == '') {            obj.data.currentNum = '0';          }          break;        case '.':          if (obj.data.currentNum.indexOf('.') == -1) { // 判断是否已包含“.”            obj.data.currentNum += btn_num          }          break;      }    }    obj.setData({      screenNum: obj.data.currentNum    })  },})