In previous applications, most of the applications were in forward search. That is, there is a specific content qualification on the right side of the lookup content, such as the following example:
Copy Code code as follows:
var str3 = ' Cpu:intel Core2 5200; Memory:2g;os:ubuntu 9.04 ';
var reg3 =/memory\:\s+ (. * (? =\;os\:))/gim;
Str3.match (REG3);
alert (regexp.$1); The result is 2G.
(. * (? =\;os\:) is a typical forward lookup, only the right content is "; OS:" will be matched to.
But now to achieve the effect, the left side of the content is fixed, not to the right. However, JavaScript does not support reverse lookup. I believe that a careful friend has found that the above example has reached this goal (the previous memory\:\s+ defines the left side of the content). An example is given below:
Copy Code code as follows:
Program purpose, remove the domain name in the image path
var str = ' ';
var reg1 =/(\Str.match (REG1);
Alert (str.replace (regexp.$4, '));
So is there a reverse pre-search? The answer is yes, but the reality is brutal. I looked up some information, which mentioned the reverse pre-search in the form of <= or <!. As a guide. Unfortunately, JavaScript is not supported and has been supported in a later version of Java, so the following test program (JRE1.6.0_03) is written:
Copy Code code as follows:
Import Java.util.regex.Matcher;
Import Java.util.regex.Pattern;
public class Regexptest {
public static void Main (string[] args) {
Pattern P = pattern.compile ((? <=\\Matcher Matcher = P.matcher ("System.out.println (Matcher.matches ());
}
}
The program itself should have no problems, but the results of the operation:
Exception in thread ' main ' java.util.regex.patternsyntaxexception:look-behind group does not have an obvious maximum Th near Index 27
((? <=\
I google for a long time, the end of the only result is to change the way the wording. Hope to see this article friend, if already realized this kind of effect, must leave a message hesitate enlighten.
Also, when I look at the document, I see it: the regular expression of the boot, which says "match does not store", baffled. Feel or code to the reality, write a look at:
Copy Code code as follows:
var str2 = ' client name ';
var REG2 =/(client name (?: Said)?) /;
Str2.match (REG2);
alert (regexp.$1); Client Name
alert (regexp.$2); Empty string
Do not use?:
REG2 =/(client name (called)?) /;
Str2.match (REG2);
alert (regexp.$1); Client Name
alert (regexp.$2); Said
Agile development Theory says: Code is the best document. Gave me an excuse, hehe.
