In the clusterBuilder() function inside the evidence service, when we pushed a new element to the observations array, we used the article key - generated by Firebase - as the value for the "id" property in each observation element:
// src/app/evidence/evidence.service.ts line number: 344
observations[word].push({
id: article.key, //...
});
But we never used that value. Technically, we could use that id as the node id, but for the sake of simplicity and easier debugging we didn't.
Tip
If you want to use article ids, keep in mind that graph node ids should be unique, otherwise you will get an error message from VisJs. In our case, that means the same article cannot appear on two or more clusters. So if you want to use the article id as the node id, make sure that you have a code that checks for duplicates and deals with them before adding a new node to the network.
Now it is time to put the article id (that we never used before) in better use...