Fill in a text field with a file system path

I have an HTML form and one the pieces of data we are collecting is a folder location. Right now the users have to manually input the path. I've been asked to make this easier. My thought was to provide a file input field, and have the user select a file in the needed folder, and then use javascript to parse the full file system path, and populate the other开发者_开发问答 field. The product owners seemed to like that idea. Since I have been trying to come up with some javascript to do this, and haven't been very successful. Any recommendations?

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