Js的学习第五天

依旧是课堂的内容

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <a>一个数：</a><input type="text" id="num1" /><br>
    <a>另一个数：</a><input type="text" id="num2" /><br>
    <input type="button" value="相加" onclick="oldofnew('+')">
    <input type="button" value="相减" onclick="oldofnew('-')">
    <input type="button" value="相乘" onclick="oldofnew('*')">
    <input type="button" value="相除" onclick="oldofnew('/')">
    <br>
    <a>结果：</a><input type="text" id="newnum" />
    <script>
        function oldofnew(x){
        // 这个地方做输入判断，对输入的value进行里面是否有非法字符
        // var re = /^-.?[0-9]+.?[0-9]*$/;
        // 如果是判断正整数
        // var re = /[0-9]+[0-9]*]*/;
        // 上面注释掉的方法不好，别使用
        var num11= document.getElementById("num1").value
        var num22= document.getElementById("num2").value
        // 这个方法可以正确区分数字和字符，同时，不会对科学技术法产生影响
        if (isNaN(num11) ||  isNaN(num22))
            alert("非法字符");
        else switch(x){
                case '+':var sumnum = Number(document.getElementById("num1").value) +Number(document.getElementById("num2").value);
                document.getElementById("newnum").value=sumnum;break;
                case '-':var sumnum = Number(document.getElementById("num1").value) -Number(document.getElementById("num2").value);
                document.getElementById("newnum").value=sumnum;break;
                case '*':var sumnum = Number(document.getElementById("num1").value) *Number(document.getElementById("num2").value);
                document.getElementById("newnum").value=sumnum;break;
                // case '/':var sumnum = Number(document.getElementById("num1").value) /Number(document.getElementById("num2").value);
                // document.getElementById("newnum").value=sumnum;break;
                case '/':
                    if(Number(document.getElementById("num2").value)==0){
                        alert("被除数不能是0");
                    }
                    else{
                        var sumnum = Number(document.getElementById("num1").value) /Number(document.getElementById("num2").value);
                        document.getElementById("newnum").value=sumnum;break;
                    }     
            }
        }
    </script>
</body>
</html>
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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <h1>大小写转换</h1><br>
    <a>原数据：</a><input type="text" id="oldword"/><br>
    <a>操作：</a><input type="button" onclick="oldofnew(1)" value="转大写" />
    <input type="button" onclick="oldofnew(2)" value="转小写"><br>
    <a>新数据：</a><input type="text" id="newword"/>
    <script>
        // document.getElementById("oldword").value;
        function oldofnew(s){
            switch(s){
                case 1: var new1 =  document.getElementById("oldword").value.toUpperCase();document.getElementById("newword").value=new1;break;
                case 2: var new2 = document.getElementById("oldword").value.toLowerCase();document.getElementById("newword").value=new2;
            }
        }
        // function oldofnew1(){
        //     var new1 =  document.getElementById("oldword").value.toUpperCase();
        //     document.getElementById("newword").value=new1;
        // }
        // function oldofnew2(){
        //     var new2 = document.getElementById("oldword").value.toLowerCase();
        //     document.getElementById("newword").value=new2;
        // }
    </script>
</body>
</html>