Скачать или смотреть How to Download and Process GTFS Zip Files in JavaScript

Learn how to effectively download, unzip, and handle GTFS data using JavaScript, resolving common pitfalls through practical coding examples.
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How to Download and Process GTFS Zip Files in JavaScript

Transporting data effectively is key to developing applications that rely on public transit information. If you're working with General Transit Feed Specification (GTFS) data, you may find yourself needing to download, unzip, and process a GTFS ZIP file. While the downloading and unzipping may seem straightforward, integrating the data can be tricky and often leads to common errors if not done correctly.

The Problem

You are trying to process data from a GTFS ZIP file in JavaScript using the gtfs-utils module, but encountering an issue during processing. Your script successfully downloads and unzips the file, but when you attempt to use the TXT files in your gtfsFunc() function, you get an "undefined" output.

Your initial approach involved filtering stops with a route_id, but the stops file does not contain this field. Here’s how to identify and resolve the issues to effectively utilize the GTFS data.

Solution Breakdown

1. Understanding GTFS Files

GTFS files typically include several TXT files containing various information about transit routes, stops, trips, and more. In order to successfully filter the data, it’s crucial to understand the structure of these files:

Important Fields in stops.txt

The stops.txt file contains the following fields:

stop_id

stop_name

stop_lat

stop_lon

stop_code

location_type

parent_station

wheelchair_boarding

stop_direction

2. Identifying the Right File for Filtering

Since your initial attempt to filter stops using route_id from stops.txt was unsuccessful (because that field does not exist), you should consider using data from trips.txt instead since it includes the route_id field.

Modifying the Function to Read Trips

To access the trips data, make use of the readTrips() function from the gtfs-utils library as follows:

[[See Video to Reveal this Text or Code Snippet]]

3. Updating the gtfsFunc() Method

Replace your existing gtfsFunc() function with this adapted code:

[[See Video to Reveal this Text or Code Snippet]]

4. If You Prefer stops.txt

If your intent is to work with stops.txt instead, you need to adjust your filter to something valid, like stop_name. Here is how you can modify the filter:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By understanding the structure of GTFS files and appropriately filtering the data, you can efficiently download, unzip, and process transit information using JavaScript. Make sure to leverage the correct fields in the relevant files to avoid common pitfalls such as undefined outputs.

With this guide, you should be able to tackle GTFS data handling successfully. Happy coding!