<!DOCTYPE html><html> <head> <title> 事件</title> <script type="text/javascript"> function count(){ //获取第一个输入框的值 var i=document.getElementById('txt1').value; //获取第二个输入框的值 var j=document.getElementById('txt2').value; //获取选择框的值 var k=document.getElementById('select').value; //获取通过下拉框来选择的值来改变加减乘除的运算法则 var sum; switch(k){ case "+": sum=parseInt(i)+parseInt(j); break; case "-": sum=parseInt(i)-parseInt(j); break; case "*": sum=parseInt(i)*parseInt(j); break; case "/": sum=parseInt(i)/parseInt(j); break;} //设置结果输入框的值 document.getElementById("fruit").value = sum; } </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() /> <input type='text' id='fruit' /> </body></html>
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