JS一些简单的计算题

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<!doctype html>
<html>
    <head>
    <meta charset="utf-8">
    <title>document</title>
    <style type="text/css">
/*计算器的style*/
.jisuanqi {
    width: 270px;
    height: 200px;
    border: 1px solid black;
    list-style-type: none;
    background: #C9E495;
    margin: 10px 0px 10px 0px;
}
.jisuanqi span {
    width: 20px;
    height: 10px;
    margin-right: 5px;
}
.jisuanqi input {
    margin-bottom: 5px;
}
[name=yunsuanfu] {
    width: 50px;
    height: 30px;
    margin-left: 10px;
}
/*一元二次函数求根style*/
.box {
    width: 300px;
    height: 200px;
    border: 1px solid black;
    text-align: center;
    background: #C9E495;
}
.box input {
    margin-bottom: 10px;
}
</style>
    <script type="text/javascript">
    //计算10-100之和
    function Sum(){
        var i=0;
        for (var j=10;j<=100;j++){
            i+=j;
        }
        document.getElementById("count").value=i;
    }
    //判断是否闰年
    function Runnian() {
        var year = document.getElementById("year").value;
        if (year==""){
            alert("请先输入年份");
        }
        else if (year<=0){
            alert("请输入大于0的年份");
        }
        else if ((year % 4 == 0) && (year % 100 != 0 || year % 400 == 0)){
            document.write(year+"是闰年"+"\n");
            document.write("<a href=''>返回重新输入</a>")
        }
        else{
            document.write(year+"不是闰年"+"\n");
            document.write("<a href=''>返回重新输入</a>")
        }
    }
    //计算器1
    function Calculate (){
        var sum=0;
        var num1 = parseFloat(document.getElementById("text1").value);
        var num2 = parseFloat(document.getElementById("text2").value);
        var sel = document.getElementById("select").value;
        switch(sel){
            case "+":sum=num1+num2;break;
            case "-":sum=num1-num2;break;
            case "*":sum=num1*num2;break;
            case "/":sum=num1/num2;break;
            default:sum="请输入数字选择运算符";break;
            }
            document.getElementById("jieguo").value = sum;
    }
        //计算器2
        function Cal(count){
            var sum;
            var num1 = parseFloat(document.getElementById("text3").value);
            var num2 = parseFloat(document.getElementById("text4").value);
            switch(count){
                case "+":sum=num1+num2;break;
                case "-":sum=num1-num2;break;
                case "*":sum=num1*num2;break;
                case "/":sum=num1/num2;break;
            }
                document.getElementById("result").value = (sum.toFixed(2));
        }
        //计算一元二次函数根
        function hanshu(){
        var a=parseFloat(document.getElementById("txta").value);
        var b=parseFloat(document.getElementById("txtb").value);
        var c=parseFloat(document.getElementById("txtc").value);
        var d=b*b-4*a*c
        var r1=(-b+Math.sqrt(d))/(2*a);
        var r2=(-b-Math.sqrt(d))/(2*a);
        document.getElementById("txt1").value=(r1.toFixed(2));
        document.getElementById("txt2").value=(r2.toFixed(2));
        }
    </script>
    </head>
    <body>
<!--第1题计算10到100之和-->
<input type="button" value="计算" onClick="Sum()" >
<input type="text" id="count" value="单击计算10-100之和">
<!--第2题判断是否为闰年-->
<p></p>
<div>判断是否为闰年:</div>
<input type="search" id="year" maxlength="4">
<input type="button" value="计算" onClick="Runnian()">
<!--第三题计算器-->
<p></p>
<input type="text" id="text1" size="5">
<select id="select">
      <option value="">选择运算符</option>
      <option value="+">+</option>
      <option value="-">-</option>
      <option value="*">*</option>
      <option value="/">/</option>
    </select>
<input type="text" id="text2" size="5">
<input type="button" value=" = " onClick = "Calculate()">
<input type="text" id="jieguo">
<!--计算器-->
<div class="jisuanqi">
      <h2>购物简易计算器</h2>
      <li><span>第一个数</span>
    <input type="search" id="text3">
  </li>
      <li><span>第二个数</span>
    <input type="search" id="text4">
  </li>
      <li>
    <input type="button" value=" + " name="yunsuanfu" onClick="Cal('+')">
    <input type="button" value=" - " name="yunsuanfu" onClick="Cal('-')">
    <input type="button" value=" × " name="yunsuanfu" onClick="Cal('*')">
    <input type="button" value=" ÷ " name="yunsuanfu" onClick="Cal('/')">
  </li>
      <li><span>计算结果</span>
    <input type="search" id="result">
  </li>
    </div>
<div class="box">
      <h3>分别输入abc求根</h3>
      <input type="text" size="3" value="" id="txta">
      <input type="text" size="3" value="" id="txtb">
      <input type="text" size="3" value="" id="txtc">
      <br />
      <input type="button" value="求根" onClick="hanshu()">
      <br />
      <input type="text" size="7" id="txt1">
      <input type="text" size="7" id="txt2">
    </div>
</body>
</html>    

原文链接:https://www.idaobin.com/archives/206.html

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