Mini Calculator(JavaScript)

< html >
     < head >
         < title > Calculator title >
         < script  language ="javascript" > ...
            
            //数字验证
            function ValidateIsNum(textbox)
            ...{
                //如果为空，则默认为０
                if(textbox.value == "")
                ...{
                    textbox.value = 0;
                    return true;
                }
                //输入为非数字则清空并提示
                if(isNaN(textbox.value))
                ...{
                    textbox.value = "";
                    alert("请输入数字");
                    textbox.focus();
                    return false;
                }
                return true;
            }
            
            //改变提示
            function ChangeTitle(radio)
            ...{
                var title1 = document.getElementById("tdTitle1");
                var title2 = document.getElementById("tdTitle2");
                if(radio.id =="plus")
                ...{                    
                    title1.innerText = "请输入加数１：";
                    title2.innerText = "请输入加数２："
                }
                if(radio.id == "minus")
                ...{                    
                    title1.innerText = "请输入被减数：";
                    title2.innerText = "请输入减数："
                }
                if(radio.id == "multiply")
                ...{                    
                    title1.innerText = "请输入被乘数：";
                    title2.innerText = "请输入乘数："
                }
                if(radio.id == "divide")
                ...{
                    title1.innerText = "请输入被除数：";
                    title2.innerText = "请输入除数："
                }
                //有输入框为空，则Focus，不为空则计算
                var text1 = document.getElementById("input1");
                var text2 = document.getElementById("input2");
                if(text1.value == "")
                    text1.focus();
                else if(text2.valuse == "")
                    text2.focus();
                    else
                        Calc(text1,text2);
            }
            
            function Calc(textbox1,textbox2)
            ...{
                //验证输入是否合法
                if(!ValidateIsNum(textbox1) || !ValidateIsNum(textbox2))
                ...{
                    return;
                }
                var operand1 = parseFloat(textbox1.value);
                var operand2 = parseFloat(textbox2.value);
                var result = 0;
                if(document.getElementById("plus").checked == true)
                ...{
                    result = operand1 + operand2;
                }
                if(document.getElementById("minus").checked == true)
                ...{
                    result = operand1 - operand2;
                }
                if(document.getElementById("multiply").checked == true)
                ...{
                    result = operand1 * operand2;
                }
                if(document.getElementById("divide").checked == true)
                ...{
                    if(operand2 != 0)
                    ...{
                        result = operand1 / operand2;
                    }
                    else
                    ...{
                        alert("被除数不可为零");
                        textbox2.value = "";
                        textbox2.focus();
                    }
                }
                //输出
                document.getElementById("inputResult").value = result;
            }
            
            //当focus时如果内容为０，则清空
            function ClearWhenFocus(textbox)
            ...{
                if(textbox.value == 0)
                ...{
                    textbox.value = "";
                }
            }
         script >
     head >
     < body >
         < table  border ="2" >
             < tr >
                 < td > 请选择运算符： td >
                 < td >
                     < input  type ="radio"  checked ="true"  id ="plus"  name ="operator"  onclick ="ChangeTitle(this)" > input > +
                     < input  type ="radio"  id ="minus"  name ="operator"   onclick ="ChangeTitle(this)" > input > -
                     < input  type ="radio"  id ="multiply"  name ="operator"   onclick ="ChangeTitle(this)" > input > *
                     < input  type ="radio"  id ="divide"  name ="operator"   onclick ="ChangeTitle(this)" > input > /
                 td >
             tr >
             < tr >
                 < td  id ="tdTitle1" > 请输入加数1 td >
                 < td >< input  type ="text"  id ="input1"  style ="display:block"  onkeyup ="Calc(this,input2)"  onfocus ="ClearWhenFocus(this)" > input > td >
             tr >
             < tr >
                 < td  id ="tdTitle2" > 请输入加数2 td >
                 < td >< input  type ="text"  id ="input2"  style ="display:block"  onkeyup ="Calc(input1,this)"  onfocus ="ClearWhenFocus(this)" > input > td >
             tr >
             < tr >
                 < td > 计算结果为： td >
                 < td >< input  type ="text"  id ="inputResult"  style ="display:block" > input > td >
             tr >
         table >
     body >
html >