Regular Expressions

[skaterdav85]

can someone help decipher this for me:stringToTrim.replace(/^\s+|\s+$/g,"");what do these characters do: ^ | $ .... I wasnt too clear on these from the tutorial

[jeffman]

In this context:^ means "at the beginning of the string" -- notice how it comes before the thing that needs to be at the beginning$ means "at the end of the string" -- notice how it comes after the thing that needs to be at the end| means "or" -- so we are looking for one thing OR the other.Altogether, we are looking for 1 or more space characters (space, tab, newline, etc) at the beginning of the string, or 1 or more space characters at the end of the string, we are looking for them globally (yes, it does matter), and we will replace each match with an empty string.Looks like a left-right trim function to me.

[skaterdav85]

could you do something like this then to remove any   from the left and right of a string, or does the string have to be special like \s?

stringToTrim = stringToTrim(/^ +| $/g,"")

[jeffman]

You can match anything with a regex. Just keep in mind what you're working with. Shortcuts like \s define character classes that have nothing to do with HTML. When you try to match an HTML entity like   you are literally looking for those six characters. So to make that work, you have to treat them as a group. You can do that with parens:re = /^( )+|( )+$/g;s = s.replace(re, ""); But be careful. This literally means at the beginning and the end. If you have a true space or a newline at the end, or right before the first  , it won't work. You can do what you want; you'll just need to tweak it.Like, if all you want to do is replace all the   characters in your string, and you don't care where they are, just use this:re =/ /g;s = s.replace(re, "");

[skaterdav85]

re = /^( )+|( )+$/g;s = s.replace(re, "");

oh ok. ya because i have   characters before and after a string that i need to trim. So to replace them, I need to put the   in between parenthesis like you did above?

[jeffman]

Yes. That tells the repetition operator (the + sign) to treat the six-character entity as a group. Otherwise, it will look for repetitions of the ; character only.Have you tried it? Is it not working?

[skaterdav85]

well evidentaly the   are only on the outsides of my string, so i just did:

string.replace(/ /g,'')

I didnt try what you wrote. I just wanted to understand what the parenthesis did. You said:

Otherwise, it will look for repetitions of the ; character only.

Why would it only look for the semi-colon and not the &,n,b,s, or p characters?

[justsomeguy]

Because when you tell it to look for this: +That's saying to look for an ampersand, followed by "n", followed by "b", followed by "s", followed by "p", followed by one or more ";". So that will match this: ;;;;;;but not this:  This pattern:( )+Tells it to look for one or more " ".

[skaterdav85]

oh ok got. thanks! you're quite the expert at js and php. You can remember all these weird looking regex details.

[Synook]

Note that regular expressions as we know them* actually come from Perl *as in PHP and JS.