Question 245515 in Javascript Question posted in
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Javascript – Regex match three words in order (there can be words in between)

I’m converting a buffer of a PDF into a string to find the page count. Here is an example of the buffer string:

<<
/Type /Pages
/Count 2
/Kids[4 0 R 8 0 R]
>>

I see that page count is defined after /Type /Pages and after /Count. Here is a different example:

<<
/Type /Pages
/MediaBox [ 0 0 612 792 ]
/Count 22
>>

As you can see, the count is now defined after MediaBox in between. I am trying to come up with a regex statement that can match the page count in both scenarios but I’m not sure where to start.
Would it make sense to match for 3 words in order then extract the number? Matching Type first, then Pages, then lastly Count and extract the number after?

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2

Answers


  1. 0 
    //Type /Pagesb.*?^/Count (d+)/ms

    should do it, with capture group 1 holding the value of the count.

    Demo(https://regex101.com/r/5dk3eP/1). Hover the cursor over each element of the regular expression to obtain an explanation of its function.

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  2. 0

    I would use a regex which looks for /Type and /Pages between << and >> and then captures the Count when they are both found. This will then be completely independent of the order of the tags. You can do this with a tempered greedy token which prevents matching beyond >>:

    <<(?=(?:(?!>>).)*/Type)(?=(?:(?!>>).)*/Pages)(?:(?!>>).)*/Counts+(d+)

    For sample data of:

    <<
/Type /Pages
/Count 2
/Kids[4 0 R 8 0 R]
>>
<<
/Type /Pages
/MediaBox [ 0 0 612 792 ]
/Count 22
>>
<<
/Type /Image
/MediaBox [ 0 0 612 792 ]
/Count 1
>>
1 0 obj <</Type /Pages /Kids [3 0 R ] /Count 1 >>
2 0 obj <<   /Count 1   /Kids [ 5 0 R ]   /Type /Pages >>

    Group 1 will contain [2, 22, 1, 1]

    Demo on regex101. Note you need the s regex flag to make . match newlines as well.

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