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Thread: Reg Exp: Newbie Question

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  1. #1
    Join Date
    Sep 2009
    Posts
    51

    Reg Exp: Newbie Question

    Hi,

    Sorry, a newbie question here:

    I encountered the following code:

    Code:
    var temp = somestring;
    temp = temp.replace( /^\s*/, "" );
    temp = temp.substring(0,6);

    Doesn't this mean replace zero or more occurrences of non-whitespace with the empty string?

    If so, I don't see how the 3rd line of code will ever return anything but whitespace. Am I off the mark?

  2. #2
    Join Date
    Jun 2003
    Location
    here
    Posts
    4,551
    That's something confusing with regExps, the carat can either represent the start of a line(or in multiline mode the start of the whole string) OR mean not.
    In general if it comes first it means the former, if it occurs later on it means the later, but there are several complex rules that define this.
    If you are using PHP please use the [PHP] and [/PHP] forum tags for highlighting...
    The same applies to HTML and the forums [HTML][/HTML] tags.

  3. #3
    Join Date
    Sep 2009
    Posts
    51
    I read up on it - it seems that the big difference is whether the caret is used inside square brackets or outside. Inside it negates the character class. Outside it marks the beginning of the string. So in my example the expression means "trim all whitespace from the beginning of the line".

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