<!DOCTYPE html><html> <head> <title> 事件</title> <script type="text/javascript"> function count(){ var abb1=document.getElementById("txt1").value; var abb2=document.getElementById("txt2").value; var abb3=document.getElementById("select").value; swith(abb3) { case "+":var num3 = parseInt(abb1) + parseInt(abb2);break; case "-":var num3 = parseInt(abb1) + parseInt(abb2);break; case "*":var num3 = parseInt(abb1) + parseInt(abb2);break; case "/":var num3 = parseInt(abb1) + parseInt(abb2);break; }//获取通过下拉框来选择的值来改变加减乘除的运算法则 document.getElementById("fruit").value = num3; //设置结果输入框的值 } </script> </head> <body> <input type='text' id='txt1' /> <select id='select'> <option value='+'>+</option> <option value="-">-</option> <option value="*">*</option> <option value="/">/</option> </select> <input type='text' id='txt2' /> <input type='button' value=' = ' onclick=count()/> <!--通过 = 按钮来调用创建的函数，得到结果--> <input type='text' id='fruit' /> </body></html>
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guozhchun
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<input type='button' value=' = ' onclick=count()/> <!-- onclick 后面加引号：onclick = "count()" -->
swith(abb3) // switch 单词写错
{
case "+":var num3 = parseInt(abb1) + parseInt(abb2);break;
case "-":var num3 = parseInt(abb1) + parseInt(abb2);break; // 表达式中运算符写错
case "*":var num3 = parseInt(abb1) + parseInt(abb2);break; // 表达式中运算符写错
case "/":var num3 = parseInt(abb1) + parseInt(abb2);break; // 表达式中运算符写错，PS：考虑一下除0情况
}
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