Portable MongoDB?

I have been wondering if it is possible to have a portable MongoDB instance.

My goal is making a full Javascript + HTML5 application, and store data in a /data folder, and each collection would be a .json file, but hardcoding a literal database would be certainly reinventing the wheel (or steel).

I googled some Javascript-made JSON databases as a reference, but my eyes shine on BSON data formats.

Is that possible? Or better, am I missing another mind-breaking technology that would fit my needs?

Thanks!

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