var
str1 =
"bedroom"
;
str2 =
"bedding"
reBed = /(bed(?=room))
///在我们捕获bed这个字符串时,抢先去看接下来的字符串是不是room
alert(reBed.test(str1));
//true
alert(RegExp.$1)
//bed
alert(RegExp.$2 ===
""
)
alert(reBed.test(str2))
//false
来源: