<!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>JS基础</title> <script type="text/javascript"> var a,b,sum; var a = 5; var b = 100%7; sum = a > b && a*b > 0 ; document.write( "我认为 a 的值是:" + a + " b的值是:" + b + "sum 的值是:" + sum +"<br/>"); document.write( "答案是,第一轮计算后,a 为:"+ a +";b为:"+b +";第一次计算sum为:"+ sum +"<br/>"); sum = ( (++a) + 3 ) / (2 - (--b) ) * 3; document.write( "再一次计算后,我认为 a 的值是:" + a + " b的值是:" + b + "sum 的值是:" + sum +"<br/>"); document.write( "答案是,第二轮计算后,a 为:" + a + ";b为:" + b +";第二次计算sum为:"+ sum +",sum的类型也发生变化了。"); </script> </head> <body> </body> </html>
如图所示
请说明什么问题?