How to Use Conditional Where Clauses to Filter Firestore Documents?

Using Conditional Where Clauses in Firestore

Firestore provides the where clause to filter database documents based on specified conditions. However, when dealing with dynamic filters involving multiple criteria, constructing conditional where clauses becomes necessary.

To add conditional where clauses, you can use the Query object returned by the collection() method in Firestore. The Query object is immutable, meaning each where clause operation creates a new instance.

Example:

Consider a filter for a list of books where you can specify colors, authors, and categories. Each of these criteria can have multiple values.

Book > Red, Blue > Adventure, Detective

To apply conditional where clauses for this filter, you can follow the following steps:

<code class="javascript">var query = firebase.firestore().collection("book");

// Apply color filter
if (color) {
  query = query.where("color", "in", color);
}

// Apply category filter
if (category) {
  query = query.where("category", "in", category);
}

// Apply author filter
if (author) {
  query = query.where("author", "in", author);
}

// Order by date
query = query.orderBy("date");

// Get results
query.get().then(...)</code>

This approach allows you to dynamically add or remove where clauses based on your conditional criteria.

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