<!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 num1 = parseInt(document.getElementById("txt1").value); //获取第二个输入框的值 var num2 = parseInt(document.getElementById("txt2").value) //获取选择框的值 var select = 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=0; switch(select){ case '+': sum = (num1+num2); break; case '-': sum = (num1-num2); break; case '*': sum = (num1*num2); break; case '/': sum = (num1/num2); break; default: sum = 0; break; } 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()"/> <!--通过 = 按钮来调用创建的函数，得到结果--> <input type="text" id="fruit" value="" /> </body></html>
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