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javascriptjsonparsingstring-parsing

Parsing a string into a custom object based on different criteria

As part of a small project I'm working on, I need to be able to parse a string into a custom object, which represents an action, date and a few other properties. The tricky part is that the input string can come in a variety of flavors that all need to be properly parsed.

Input strings may be in the following formats:

Go to work tomorrow at 9am

  • Wash my car on Monday, at 3 pm
  • Call the doctor next Tuesday at 10am
  • Fill out the rebate form in 3 days at 2:30pm
  • Wake me up every day at 7:00am

And the output object would look something like this:

{
   "Action":"Wash my car",
   "DateTime":"2011-12-26 3:00PM", // Format is irrelevant at this point
   "Recurring":False,
   "RecurranceType":""
}

At first I thought of constructing some sort of tree to represent different states (On, In, Every, etc.) with different outcomes and further states (candidate for a state machine, right?). However, the more I thought about this, the more it started looking like a grammar parsing problem. Due to a (limited) number of ways the sentence could be formed, it looks like some sort of grammar parsing algorithm would need to be implemented.

In addition, I'm doing this on the front end, so JavaScript is the language of choice here. Back end will be written in Python and could be used by calling AJAX methods, if necessary, but I'd prefer to keep it all in JavaScript. (To be honest, I don't think the language is a big issue here).

So, am I in way over my head? I have a strong JavaScript background, but nothing beyond school courses when it comes to language design, parsing, etc. Is there a better way to solve this problem? Any suggestions are greatly appreciated.

Solution

  • I don't know a lot about grammar parsing, but something here might help.

    My first thought is that your sentence syntax seems to be pretty consistent

    1st 3-4 words are generally VERB text NOUN, followed by some form of time. If the total options are limited to what form the sentence can take, you can hard-code some parsing rules.

    I also ran across a couple of js grammar parsers that might get you somewhere:

    http://jscc.jmksf.com/ http://pegjs.majda.cz/ http://www.corion.net/perl-dev/Javascript-Grammar.html

    This is an interesting problem you have. Please update this with your solutions later.