generic regexp using jquery variable to replace dot, colon or any other character

Question

I have a jquery code that trims the leading and trailing character (passed from the calling program). I am using a variable in RegExp to replace the character with blank. How can I make the RegExp work for any character passed from the calling program? Here is the simplified code:

var time = ":1h:45m:34s:";
var chr= ':'; //can have . or , or any other character
var regex = new RegExp("(^" + chr + ")|(" + chr+ "$)" , "g"); //works for colon but not for dot.
//var regex = new RegExp("(^/" + chr + ")|(/" + chr+ "$)" , "g"); //for dot I added / but not for colon.
var formattedtime = time.replace(regex, "");

Expected Outputs:

1. time = ":1h:45m:34s:"; 
chr = ":";
Output: 1h:45m:34s
2. time = "1h:45m:34s"; 
chr = ":";
Output: 1h:45m:34s
3. time = ".45m.34s"; 
chr = ".";
Output: 45m.34s
4. time = "1h.45m.34s."; 
chr = ".";
Output: 1h.45m.34s

How can I make the regexp work for any character?

Qtax · Accepted Answer · 2012-03-08 15:42:00Z

2

You need to escape meta characters (like . and several others) to get literals. You do that by adding a backslash before them.

JS doesn't have any built in function for that, so you could use this:

function quotemeta(str){
    return str.replace(/[.+*?|\\^$(){}\[\]-]/g, '\\$&');
}

Used like so:

new RegExp("^(?:" + quotemeta(chr) + ")+|(?:" + quotemeta(chr) + ")+$" , "g");

edited Mar 8, 2012 at 15:42

answered Mar 8, 2012 at 15:31

Qtax

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4 Comments

Sri Reddy Over a year ago

I did that as in the commented line in my code snippet. var regex = new RegExp("(^/" + chr + ")|(/" + chr+ "$)" , "g"); This works great for dot but not for colon. You mean I have to check the character and escape for each???

Qtax Over a year ago

/ is not a backslash, \ is. But you can't use it on every character, because they have special meaning, eg \s means any white space.

Sri Reddy Over a year ago

Ah, this utility method is great. It can handle many characters. More generic approach. How can I understand the RegExp you provided?

Qtax Over a year ago

It just matches any number of those characters at the beginning or end of string. I used a non-capturing group (?:...) in case it's not just one character, but a string. If you want to remove many different characters at once you can use a character class instead of the group, like [abc] will match one of a, b or c.

pät · Accepted Answer · 2012-03-08 15:33:27Z

0

var chr= ':/';
...    
var regex = new RegExp("(^[" + chr + "])|([" + chr+ "]$)" , "g");

answered Mar 8, 2012 at 15:33

pät

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4 Comments

Sri Reddy Over a year ago

This is a cool solution. It works for me. I am not that good with RegExp. Do you mind explaining this?

pät Over a year ago

Use [] to define a set of characters, eg [:/.] matches on : / or .

pät Over a year ago

I think I misunderstood your question, as I thought you wanted to remove a set of characters by using only one expression.

Sri Reddy Over a year ago

Pat, sorry if I made it sound silly.. Qtax's solution seems to be working for various characters and I wanted a generic solution to handle different characters. Thanks for your time.

Siva Charan · Accepted Answer · 2012-03-08 16:36:49Z

0

Regex should this way:-

For Colon, /^(\:)|(\:)$/gim

For Dot, /^(\.)|(\.)$/gim

OR

/^(\:|\w|\.)|(\:|\w|\.)$/gim

LIVE DEMO

edited Mar 8, 2012 at 16:36

answered Mar 8, 2012 at 15:36

Siva Charan

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