js实现简单计算器

参考部分资料，编写一个简单的计算器案例，虽然完成了正常需求，但是也有不满之处，待后续实力提升后再来补充，先把不足之处列出：

　　1：本来打算只要打开页面，计算器的输入框会显示一个默认为0的状态，但是在输入框加入默认显示为0的时候，选择数据输入时，该0会显示输入数字的前面，例如”0123“，由于能力有限，待后续实力提升再来补充完善！

　　2：目前只能实现鼠标控制选择按钮，待完善键盘录入功能。

　　3：乘法的那个符号在本来想改成”ד这个符号的，待后续完善。

　　附图片一张：

　　html部分：

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>计算器</title>
</head>
<body onload="onLoad()">
<div id="calculator">
  <div class="LOGO">
    <span class="name">简单的计算器</span>
    <span class="verson">@liumobai v1.0</span>
  </div>
  <div id="shuRu">
    <!--screen输入栏-->
    <div class="screen">
      <input type="text" id="screenName" name="screenName" class="screen" value="" onfocus="jsq(this)">
    </div>
  </div>
  <div id="keys">
    <!-- operators and other keys -->
    <!--第一排-->
    <input type="button" id="7" onclick="jsq(this.id)" value="7" class="buttons">
    <input type="button" id="8" onclick="jsq(this.id)" value="8" class="buttons">
    <input type="button" id="9" onclick="jsq(this.id)" value="9" class="buttons">
    <input type="button" id="Back" onclick="tuiGe()" value="Back" class="buttons">
    <input type="button" id="C" onclick="clearNum()" value="C" class="buttons" style="margin-right:0px">
    <!--第二排-->
    <input type="button" id="4" onclick="jsq(this.id)" value="4" class="buttons">
    <input type="button" id="5" onclick="jsq(this.id)" value="5" class="buttons">
    <input type="button" id="6" onclick="jsq(this.id)" value="6" class="buttons">
    <input type="button" id="*" onclick="jsq(this.id)" value="*" class="buttons">
    <input type="button" id="/" onclick="jsq(this.id)" value="/" class="buttons" style="margin-right:0px">
    <!--第三排-->
    <input type="button" id="1" onclick="jsq(this.id)" value="1" class="buttons">
    <input type="button" id="2" onclick="jsq(this.id)" value="2" class="buttons">
    <input type="button" id="3" onclick="jsq(this.id)" value="3" class="buttons">
    <input type="button" id="+" onclick="jsq(this.id)" value="+" class="buttons">
    <input type="button" id="-" onclick="jsq(this.id)" value="-" class="buttons" style="margin-right:0px">
    <!--第四排-->
    <input type="button" id="0" onclick="jsq(this.id)" value="0" class="buttons">
    <input type="button" id="00" onclick="jsq(this.id)" value="00" class="buttons">
    <input type="button" id="." onclick="jsq(this.id)" value="." class="buttons">
    <input type="button" id="%" onclick="jsq(this.id)" value="%" class="buttons">
    <input type="button" id="eva" onclick="eva()" value="=" class="buttons" style="margin-right:0px">
  </div>
  <div class="footer">
    <span class="aside">欢迎使用JavaScript计算器</span>
      <span class="link">
        <a href="#" title="声明" target="_blank">反馈</a>
      </span>
  </div>
</div>
</body>
</html>

　　JS部分：

<script>
  var num = 0; // 定义第一个输入的数据
  function jsq(num) {
    //获取当前输入
    document.getElementById('screenName').value += document.getElementById(num).value;
  }
  function eva() {
    //计算输入结果
    document.getElementById("screenName").value = eval(document.getElementById("screenName").value);
  }
  function clearNum() {
    //清0
    document.getElementById("screenName").value = null;
    document.getElementById("screenName").focus();
  }
  function tuiGe() {
    //退格
    var arr = document.getElementById("screenName");
    arr.value = arr.value.substring(0, arr.value.length - 1);
  }
  function onLoad(){
    //加载完毕后光标自动对应到输入框
    document.getElementById("screenName").focus();
  }
</script>

　　CSS部分：　

/*Basic reset*/
*{
  margin:0;
  padding:0;
  box-sizing: border-box;
  font: 14px Arial,sans-serif;
}
html{
  height:100%;
  background-color:lightslategrey;
}

#calculator{
  margin: 15px auto;
  width:330px;
  height:400px;
  border: 1px solid lightgray;
  background-color:darkgrey;
  padding:15px;
}

/*LOGO*/
.LOGO{
  height:20px;

}
.LOGO .name{
  float:left;
  line-height:30px;
}
.LOGO .verson{
  float:right;
  line-height:30px;
}
/*screen*/
#shuRu{
  margin-top:15px;
}
.screen{
  margin-top:5px;
  width:300px;
  height:40px;
  text-align: right;
  padding-right:10px;
  font-size:20px;
}
#keys{
  border:1px solid lightgray;
  height:223px;
  margin-top:25px;
  padding:8px;
}
#keys .last{
  margin-right:0px;
}
.footer{
  margin-top:20px;
  height:20px;
}
.footer .link{
  float:right;
}

#keys .buttons{
  float:left;
  width: 42px;
  height: 36px;
  text-align:center;
  background-color:lightgray;
  margin: 0 17px 20px 0;
}

接下来再给大家分享一则实例

<html>
<head>
    <title>Untitled</title>
    <style type="text/css">
       input[type=button]
       {
           width:25px;
           height:25px;
       }
    </style>
    <script type="text/javascript">
       var result=0;
      var point=false;       //判断是小数点前还是后
      var multiple=0.1;         //初始化小数点后的倍率
      var sort=0;              //标记加减乘除
      var temp=0;                //记录上一轮结果
      function onbutton0()    //数字按钮动作
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+0;       //小数点前的处理
           else                                    //小数点后的处理
           {
              result=result+multiple*0;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton1()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+1;
           else
           {
              result=result+multiple*1;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton2()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+2;
           else
           {
              result=result+multiple*2;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton3()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+3;
           else
           {
              result=result+multiple*3;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton4()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+4;
           else
           {
              result=result+multiple*4;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton5()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+5;
           else
           {
              result=result+multiple*5;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton6()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+6;
           else
           {
              result=result+multiple*6;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton7()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+7;
           else
           {
              result=result+multiple*7;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton8()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+8;
           else
           {
              result=result+multiple*8;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton9()
       {
         var name=document.getElementByIdx_x("show");
           if(!point) result=10*result+9;
           else
           {
              result=result+multiple*9;
              multiple=multiple*0.1;
           }
           name.value=String(result);
       }
       function onbutton_point()           //小数点按钮
       {
          var name=document.getElementByIdx_x("show");
           point=true;
           name.value=String(result)+".";
       }
       function onbutton_back()        //退格按钮
       {
           var name=document.getElementByIdx_x("show");
           var temp=name.value;
           name.value="";
           for(var i=0;i<temp.length-1;i++)
              name.value+=temp[i];
       }
       function onbutton_plus()
       {
           var name=document.getElementByIdx_x("show");
           point=false;
           multiple=0.1;
           switch (sort)                       //遇到下一个操作符时判断上一个操作符是什么，并进行上一个操作符的计算
           {                                  //eg:1+2+3=  遇到第二个+时判断前一个符号，发现是+则进行+运算，得到3赋给result
              case 1:result=result+temp;
                   break;
              case 2:result=temp-result;
                   break;
              case 3:result=temp*result;
                   break;
              case 4:result=temp/result;
                   break;
           }
           sort=1;
           temp=result;
           result=0;
           name.value="0";
       }
       function onbutton_minus()
       {
           var name=document.getElementByIdx_x("show");
           point=false;
           multiple=0.1;
           switch (sort)
           {
              case 1:result=result+temp;
                   break;
              case 2:result=temp-result;
                   break;
              case 3:result=temp*result;
                   break;
              case 4:result=temp/result;
                   break;
           }
           sort=2;
           temp=result;
           result=0;
           name.value="0";
       }
       function onbutton_mult()
       {
           var name=document.getElementByIdx_x("show");
           point=false;
           multiple=0.1;
           switch (sort)
           {
              case 1:result=result+temp;
                   break;
              case 2:result=temp-result;
                   break;
              case 3:result=temp*result;
                   break;
              case 4:result=temp/result;
                   break;
           }
           sort=3;
           temp=result;
           result=0;
           name.value="0";
       }
       function onbutton_div()
       {
           var name=document.getElementByIdx_x("show");
           point=false;
           multiple=0.1;
           switch (sort)
           {
              case 1:result=result+temp;
                   break;
              case 2:result=temp-result;
                   break;
              case 3:result=temp*result;
                   break;
              case 4:result=temp/result;
                   break;
           }
           sort=4;
           temp=result;
           result=0;
           name.value="0";
       }
       function onbutton_equal()
       {
           var name=document.getElementByIdx_x("show");
           point=false;                //重置
           multiple=0.1;               //重置
           switch (sort)
           {
              case 1:result=result+temp;
                   break;
              case 2:result=temp-result;
                   break;
              case 3:result=temp*result;
                   break;
              case 4:result=temp/result;
                   break;
           }
           sort=0;                       //重置
           temp=result;
           result=0;
           name.value=String(temp);
       }
       function onbutton_clear()   //重置为初始状态
       {
           result=0;
         point=false;
         multiple=0.1;        //初始化小数点后的倍率
         sort=0;             //标记加减乘除
         temp=0;               //记录上一轮结果
         var name=document.getElementByIdx_x("show");
         name.value="0";
       }
    </script>
</head>

<body>
    <table align="center">
      <tr>
        <td colspan="5"><input type="text" value="0" id="show"></td>
      </tr>
      <tr>
         <td><input type="button" value="7" onclick="onbutton7();"></td>
         <td><input type="button" value="8" onclick="onbutton8();"></td>
         <td><input type="button" value="9" onclick="onbutton9();"></td>
         <td><input type="button" value="/" onclick="onbutton_div();"></td>
         <td><input type="button" value="<" onclick="onbutton_back();"></td>
      </tr>
      <tr>
        <td><input type="button" value="4" onclick="onbutton4();"></td>
         <td><input type="button" value="5" onclick="onbutton5();"></td>
         <td><input type="button" value="6" onclick="onbutton6();"></td>
         <td><input type="button" value="*" onclick="onbutton_mult();"></td>
         <td><input type="button" value="C" onclick="onbutton_clear();"></td>
      </tr>
      <tr>
        <td><input type="button" value="1" onclick="onbutton1();"></td>
         <td><input type="button" value="2" onclick="onbutton2();"></td>
         <td><input type="button" value="3" onclick="onbutton3();"></td>
         <td><input type="button" value="-" onclick="onbutton_minus();"></td>
         <td rowspan="2"><input type="button" value="=" style="width:25px;height:57px;" onclick="onbutton_equal();"></td>
      </tr>
      <tr>
        <td colspan="2"><input type="button" value="0" style="width:57px;height:25px;" onclick="onbutton0();"></td>
         <td><input type="button" value="." onclick="onbutton_point();"></td>
         <td><input type="button" value="+" onclick="onbutton_plus();"></td>
      </tr>
   </table>
</body>
</html>