Firebase search by child value

A warning to avoid unpleasant surprises: when you use orderByChild and equalTo do not forget to add an index on your data (here's the doc)

If you don't all the nods will be downloaded and filtered client side which can become very expensive if your database grows.

You can use equalTo() to find any child by value. In your case by name:

ref.child('users').orderByChild('name').equalTo('John Doe').on("value", function(snapshot) {
    console.log(snapshot.val());
    snapshot.forEach(function(data) {
        console.log(data.key);
    });
});

The purpose of orderByChild() is to define the field you want to filter/search for. equalTo() can get an string, int and boolean value.

Also can be used with auto generated keys (pushKey) too.

You can find all the documentation here