微信小程序计数器代码（微信小程序实现计算器案例）

<!--pages/index/index.wxml-->
<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="dotBtn">.</view>
    <view hover-class="bg" bindtap="opBtn" data-val="=">=</view>
  </view>
</view>

/* pages/index/index.wxss */

page {
  display: flex;
  flex-direction: column;
  height: 100%;
  color: #555;
}

.result {
  flex: 1;
  background: #f3f6fe;
  position: relative;
}

.result-num {
  position: absolute;
  font-size: 27pt;
  bottom: 5vh;
  right: 3vw;
}

.result-op {
  font-size: 15pt;
  position: absolute;
  bottom: 1vh;
  right: 3vw;
}

.btns {
  flex: 1;
}

/* 按钮样式 */

.bg {
  background: rgb(223, 44, 20);
}

.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-right: 1rpx solid #ccc;
  border-bottom: 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: #fc8e00;
}

// 精确计算
module.exports = {
  // 加
  add: function(arg1, arg2) {
    var r1, r2, m
    try {
      r1 = arg1.toString().split(".")[1].length
    } catch (e) {
      r1 = 0
    }
    try {
      r2 = arg2.toString().split(".")[1].length
    } catch (e) {
      r2 = 0
    }
    // 将小数都化为整数在进行计算  m是需要×的10的幂数
    m = Math.pow(10, Math.max(r1, r2))
    // 最后返回的时候再除以m
    return (arg1 * m + arg2 * m) / m
  },
  // 减
  sub: function(arg1, arg2) {
    var r1, r2, m, n
    try {
      r1 = arg1.toString().split(".")[1].length
    } catch (e) {
      r1 = 0
    }
    try {
      r2 = arg2.toString().split(".")[1].length
    } catch (e) {
      r2 = 0
    }
    m = Math.pow(10, Math.max(r1, r2))
    //动态控制精度长度
    n = (r1 >= r2) ? r1 : r2
    return ((arg1 * m - arg2 * m) / m).toFixed(n)
  },
  // 乘
  mul: function(arg1, arg2) {
    var m = 0,
      s1 = arg1.toString(),
      s2 = arg2.toString()
    try {
      m += s1.split(".")[1].length
    } catch (e) {}
    try {
      m += s2.split(".")[1].length
    } catch (e) {}
    return Number(s1.replace(".", "")) * Number(s2.replace(".", "")) / Math.pow(10, m)
  },
  // 除
  li: function(arg1, arg2) {
    var t1 = 0,
      t2 = 0,
      r1, r2
    try {
      t1 = arg1.toString().split(".")[1].length
    } catch (e) {}
    try {
      t2 = arg2.toString().split(".")[1].length
    } catch (e) {}

    r1 = Number(arg1.toString().replace(".", ""))
    r2 = Number(arg2.toString().replace(".", ""))
    return (r1 / r2) * Math.pow(10, t2 - t1)
  }
}

 // 数字按钮事件处理函数
  numBtn: function(e) {
    var num = e.target.dataset.val
    if (this.data.num === '0' || this.isClear) {
      this.setData({
        num: num
      })
      this.isClear = false
    } else {
      this.setData({
        num: this.data.num + num
      })
    }
  },

 // 运算符事件处理函数
  opBtn: function(e) {
    var op = this.data.op
    // 获取之前的数
    var num = Number(this.data.num)
    this.setData({
      op: e.target.dataset.val
    })
    if (this.isClear) {
      return
    }
    this.isClear = true
    if (this.result === null) {
      this.result = num
      return
    }
    if (op === '+') {
      this.result = calc.add(this.result, num)
    } else if (op === '-') {
      ......
      其他运算操作（详细代码看下面完整代码部分）
      ......
    }
    this.setData({
      num: this.result + ''
    })
  },

// pages/index/index.js
const calc = require('../../utils/calc.js')

Page({

  /**
   * 页面的初始数据
   */
  data: {
    num: '0',
    op: ''
  },
  // 结果
  result: null,
  // 是否清空数字行
  /*
  清空的情况(值为true)
    点击过运算符之后,改为true 以便下一次输入数字显示
    点击清空
  */
  isClear: false,

  // 数字按钮事件处理函数
  numBtn: function(e) {
    var num = e.target.dataset.val
    if (this.data.num === '0' || this.isClear) {
      this.setData({
        num: num
      })
      this.isClear = false
    } else {
      this.setData({
        num: this.data.num + num
      })
    }
  },

  // 运算符事件处理函数
  opBtn: function(e) {
    var op = this.data.op
    // 获取之前的数
    var num = Number(this.data.num)
    this.setData({
      op: e.target.dataset.val
    })
    if (this.isClear) {
      return
    }
    this.isClear = true
    if (this.result === null) {
      this.result = num
      return
    }
    if (op === '+') {
      this.result = calc.add(this.result, num)
    } else if (op === '-') {
      this.result = calc.sub(this.result, num)
    } else if (op === '*') {
      this.result = calc.mul(this.result, num)
    } else if (op === '/') {
      this.result = calc.li(this.result, num)
    } else if (op === '%') {
      this.result = this.result % num
    }
    this.setData({
      num: this.result + ''
    })
  },

  // 小数点事件处理函数
  dotBtn: function() {
    if (this.isClear) {
      this.setData({
        num: '0.'
      })
      this.isClear = false
      return
    }
    if (this.data.num.indexOf('.') >= 0) {
      return
    }
    this.setData({
      num: this.data.num + '.'
    })
  },

  // DEL按钮处理函数
  delBtn: function() {
    var num = this.data.num.substr(0, this.data.num.length - 1)
    this.setData({
      num: num === '' ? '0' : num
    })
  },

  // C按钮事件处理函数
  resetBtn: function() {
    this.result = null
    this.isClear = false
    this.setData({
      num: '0',
      op: ''
    })
  }
})