Question

Complete and utter javascript newbie here with a problem fetching .pdf files from a web server based on a partial match. I have made a program that outputs data to a webserver, and one of the components is a folder of .pdf files. I want to be able to click on a link that will pull up the corresponding .pdf file based on a value in the data table that’s generated (I’m using slickgrid for this). Each of the .pdf files contains the value that’s in the data table and serves as good query to the .pdf folder, and I’ve been successful at getting the .pdfs I want with the following code:

var value = grid.getData().getItem(row)['data'];
var locpath = window.location.pathname.substring(0,window.location.pathname.lastIndexOf('/'));
var plotsFolder = window.location.protocol + "//" + window.location.host + locpath + "/CovPlots/";
var href = plotsFolder + value + ".pdf";
return "<a href='" + href + "'>" + value + "</a>";

The catch here is that sometimes the .pdf file that’s generated is a concatenation of two or more (I’ve seen up to 4 so far) of the ‘data’ strings, separated by ‘_’ as a delimiter for reasons not worth getting into. So, if the .pdf file is ‘somestring.pdf’, I can get it without problem. However, if the .pdf file is ‘somestring_anotherstring.pdf’, I can’t figure out how to get that .pdf file if I have either ‘somestring’ or ‘anotherstring’ as the value of ‘data’.

I’ve tried a ton of different things to get some kind of lookup that I can use to pull down the correct file based on a partial match. The latest attempt is with the FilenameFilter object in javascript, but without any knowledge of javascript, I’m having a hard time to get it working. I tried to create a new function that I could call as a lookup for the .pdf URL:

function lookup() {
    File directory = new File(plotsFolder);
    String[] myFiles = directory.list(new FilenameFilter() {
        public boolean accept(File directory, String fileName) {
        return fileName.match(value);
        }
    });
}

That only seems to thrown an error. Can anyone point me in the right direction to be able to download the correct .pdf file based on a partial match? I also tried to see if there was a jquery way to do it, but couldn’t seem to find something that works. Thanks in advance!

Answer 1

Without support from the server, JavaScript cannot find a file from a partial filename. What you can do, however, is have a little script on the server that does the partial-filename-matching for JavaScript, and then JavaScript can ask the server to do the match, and then when it gets the match back, it can use that filename.

If you don’t mind loading a whole index of all the PDFs at once, you could use this little Python script to generate an index in a nice, JavaScript-friendly JSON format:

#!/usr/bin/env python
# Create an index of a bunch of PDF files.
# Usage: python make_index.py directory_with_pdf_files

import os
import sys
import json


def index(directory):
    index = {}

    for filename in os.listdir(directory):
        base, ext = os.path.splitext(filename)
        if ext.lower() != '.pdf':
            continue
        for keyword in base.split('_'):
            index[keyword] = filename

    with open(os.path.join(directory, 'index.json'), 'w') as f:
        f.write(json.dumps(index))


if __name__ == '__main__':
    index(sys.argv[1])

Then you can just load index.json with jQuery or what-have-you. When you need to find a particular PDF’s filename, you can do something like this (assuming the object loaded from index.json is in the indexOfPDFs variable):

var href = plotsFolder + indexOfPDFs[value];