求助:用JavaScript完成一个简单的计算器

<!--第一步：在<body>区域添加以下代码-->[xss_clean]<!--Beginfunctiondoit(){form.input.value=eval(form.input.value)}functionCos(){x=form.input.valueif(x=='')alert('错误:InputRequired');elseform.input.value=Math.cos(x);}functionSin(){x=form.input.valueif(x=='')alert('错误:InputRequired');elseform.input.value=Math.sin(x);}functionLn(){x=form.input.valueif(x=='')alert('错误：InputRequired');elseform.input.value=Math.log(x);}functionRoot(){x=form.input.valueif(x=='')alert('错误：InputRequired');elseform.input.value=Math.sqrt(x);}functionTan(){x=form.input.valueif(x=='')alert('错误:InputRequired');elseform.input.value=Math.tan(x);}functionIcos(){x=form.input.valueif(x=='')alert('错误:InputREquired');elseform.input.value=Math.acos(x);}functionIsin(){x=form.input.valueif(x=='')alert('Error:InputRequired');elseform.input.value=Math.asin(x);}functionItan(){x=form.input.valueif(x=='')alert('错误:InputRequired');elseform.input.value=Math.atan(x);}functionRound(){x=form.input.valueif(x=='')alert('错误:InputRequired');elseform.input.value=Math.round(x);}functionRan(){x=form.input.valueform.input.value=Math.random(x);}functionNeg(){x=form.input.valueif(x=='')警报（'错误：InputRequired'）;elsex=parseFloat（x）*-1;}functiondel(){x=form.input.valuex=(x.substring)-1}//结束-->[xss_clean]Tecool高级版计算器