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I am using Firebase as real-time DB for mobile APP I'm developing (JS Web SDK), the structure is as below in the screenshot, the key = email, each key have the mobile user information, and GPS coordination of the mobile location inside node = "path"
How to listen on all the the "path" of all the emails (users)?
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Using set() overwrites data at the specified location, including any child nodes.
You can listen to a document with the onSnapshot() method. An initial call using the callback you provide creates a document snapshot immediately with the current contents of the single document. Then, each time the contents change, another call updates the document snapshot.
After creating a new project, navigate to the Tools option on the top bar. Inside that click on Firebase. After clicking on Firebase, you can get to see the right column mentioned below in the screenshot. Inside that column Navigate to Firebase Realtime Database.
When using listeners, Firebase only sends updates to our app when data changes. Similar to OKHttp, the Firebase SDK handles all threading and asynchronicity for us, too! We just need to determine what data we'd like to listen to, and what to do when the listener returns new data.
Firebase Realtime Database is a NoSQL cloud-hosted real-time database from Google. When it comes to reading data from Firebase Realtime Database, there are two options available. The first one is to read the data using a persistent listener, meaning that we’ll always be in sync with the Firebase servers, or we can read the data only once.
In either case, Firebase interprets that the event occurs at /foo/bar , and the event data includes the old and new data at /foo/bar. If the event data might be large, consider using multiple functions at deeper paths instead of a single function near the root of your database.
For example, the before property can be used to make sure the function only uppercases text when it is first created: // Only edit data when it is first created. // Exit when the data is deleted. // Grab the current value of what was written to the Realtime Database. // writing to the Firebase Realtime Database.
Straight from the Firebase documents:
value: Read and listen for changes to the entire contents of a path.
var ref = firebase.database().ref("users");
firebase.database().ref().on('value', function(snapshot) {
// Do whatever
});
This function will run once when it is initiated and the once more for every change to the data under the path. snapshot will return all the contents of user/ which is a lot of data to be returned for every change. You can change the ref accordingly.
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