正则表达式记忆表

 

记忆表

 

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几个简单的例子(JavaScript)

 

1. + 的用法

  var pattern = /ab+g/; 

 

串	结果
"dfeoabg"	"abg"
"dfeoabfg"	null
"dfeoabbg"	"abbg"
"dfeoab"	null

 

2. ？ 的用法

  var pattern = /ab?g/; 

 

串	结果
"dfeoag"	"ag"
"dfeoabg"	"abg"
"dfeoabbg"	null
"dfeobg"	null

 

3. (?:) 的用法

  var text = "mom and dad and baby"; 

 

模式	结果
/mom ( and dad ( and baby))/	["mom and dad and baby", " and dad and baby", " and baby", index: 0, input: "mom and dad and baby"]
/mom ( and dad (?: and baby))/	["mom and dad and baby", " and dad and baby", index: 0, input: "mom and dad and baby"]
/mom(?: and dad( and baby))/	["mom and dad and baby", " and baby", index: 0, input: "mom and dad and baby"]

 

对于正则表达式 ( and baby) ，() 里的内容被捕获，反向引用时可以用上

 

而 (?: and baby) 可以简单理解成 ?: 关闭了圆括号的捕获能力，只用其来分组，所以不会占用捕获变量，也不能使用反向引用。

 

关于捕获组与反向引用可参见：http://blog.csdn.net/lxcnn/article/details/4146148