<!DOCTYPE html><html> <head> <title> 事件</title> <script type="text/javascript"> function count(){ var a; var txt1=document.getElementById("txt1").value; var txt2=document.getElementById("txt2").value; var txt3=document.getElementById("txt3").value; switch(txt3){ case "+" a=parseInt(txt1)+parseInt(txt2); break case "-" a=parseInt(txt1)-parseInt(txt2); break case "*" a=parseInt(txt1)*parseInt(txt2); break case "/" a=parseInt(txt1)/parseInt(txt2); break } document.getElementById('fruit').value=a; } </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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