Conditional Operators

RxJS's conditional operators are used to conditionally determine or evaluate the value of a stream. Such as setting a default value for an empty stream, or checking if all values satisfy a condition, they can be utilized in practical scenarios.

This page introduces each operator in three stages: "Basic Syntax and Operation," "Typical Usage Examples," and "Practical Code Examples (with UI)" in the following structure.

Understand what kind of use cases each operator is suitable for, and combining them will enable you to design reactive processing that is more robust and in line with your intentions.

NOTE

iif and defer are Creation Functions (Observable creation functions) and are not conditional operators. See Chapter 3: Creation Functions for these.

List of Operators

Below is a list of the major conditional operators and their characteristics.

Operator	Description
defaultIfEmpty	Alternative value when no value is emitted
every	Evaluate whether all values match a condition
isEmpty	Check if any value is emitted

For practical combinations and use-case based applications of operators, see the Practical Use Cases section at the end.

Be Aware of Integration with Other Categories

Conditional operators are only useful in combination with other transformation, combination, and utility operators. For example, it is common to combine them with switchMap and catchError to perform "API switching and recovery processing".

For more practical use cases, see Practical Use Cases for detailed explanations.