Ever wanted to add advanced features like geo-search to your website or app, but the process felt too overwhelming?
Well, I will let you in on a trade secret! 🤫
It can be done with JUST 9 LINES OF CODE using Firestore! 🤯
Let's get started!
Add Geo-hash to your data
Before you can use geo-search, you would need to add one additional field to your data called geohash
.
To generate the geohash
, you can use a library called geofire-common.
npm install geofire-common
The geohashForLocation
function accepts the latitude and longitude as input and returns a geohash
for the location.
await setDoc(doc(db, "cities", "LA"), {
name: "Los Angeles",
lat: 34.0,
long: -118.2,
// store geohash
geohash: geofire.geohashForLocation([lat, lng]),
});
NOTE: The geofire library is available for Swift, Kotlin, and Java too, thus enabling you to use it in your mobile apps as well.
Querying locations within a radius
After adding the geohash
to your data, you can now start querying locations from the database.
const getCitiesWithinRadius = async (
radiusInM: number,
center: [number, number]
) => {
const bounds = geofire.geohashQueryBounds(
center,
radiusInM
);
const promises = [];
for (const bound of bounds) {
const q = query(
collection(db, "cities"),
orderBy("geoHash"),
startAt(bound[0]),
endAt(bound[1])
);
promises.push(getDocs(q));
}
const snapShots = await Promise.all(promises);
const cities = snapShots
.flatMap((snapShot) => snapShot.docs)
.map((doc) => doc.data());
return cities;
};
The getCitiesWithinRadius
will accept the radius in meters and the coordinates (latitude & longitude) as input & return all the cities within the specified radius.
NOTE: To keep the code clean & easy to read, the 9 lines have been broken into several more lines, if clean code isn't your thing, you can even use a one-liner.
Limitations
As Firebase docs put it:
Edge Cases - this query method relies on estimating the distance between lines of longitude/latitude. The accuracy of this estimate decreases as points get closer to the North or South Pole which means Geohash queries have more false positives at extreme latitudes.
To remove the false positives, you can use the distanceBetween
function from the geofire-common
library to filter out the cities that are outside the radius, which would require additional computation.
const filteredCities = cities.filter((city) => {
const distanceInM = geofire.distanceBetween(
[city.lat, city.long],
center
);
return distanceInM <= radiusInM;
});
return filteredCities;
Wrapping up
Congratulations!
Now location-based search is no longer rocket science, but just a few lines of code away! 🚀
The world is your playground! 🎉
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Thanks for reading
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FAQ
These are a few commonly asked questions I get. So, I hope this FAQ section solves your issues.
-
I am a beginner, how should I learn Front-End Web Dev?
Look into the following articles: Would you mentor me?
Sorry, I am already under a lot of workload and would not have the time to mentor anyone.
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