Why Exhaustive pattern matching in Typescript? - Purpose & Use Cases

The Big Idea

What if your program silently ignores some cases and breaks later? Exhaustive pattern matching stops that before it starts!

The Scenario

Imagine you have a list of different shapes like circles, squares, and triangles, and you want to write code that does something special for each shape. Without exhaustive pattern matching, you might forget to handle one shape, and your program could behave strangely or crash.

The Problem

Manually checking each shape type with many if-else statements is slow and easy to mess up. You might miss a shape type or write duplicate code. This makes your program buggy and hard to fix.

The Solution

Exhaustive pattern matching forces you to cover every possible case. It helps your code check all shape types clearly and safely. If you forget one, the program warns you right away, so you never miss a case.

Before vs After

✗ Before

if (shape.type === 'circle') { /* handle circle */ } else if (shape.type === 'square') { /* handle square */ } // forgot triangle!

✓ After

match(shape) { case { type: 'circle' }: /* handle circle */; case { type: 'square' }: /* handle square */; case { type: 'triangle' }: /* handle triangle */; }

What It Enables

It makes your code safer and easier to maintain by ensuring every possible case is handled.

Real Life Example

When building a drawing app, you can use exhaustive pattern matching to make sure every shape type is drawn correctly, so users never see missing or broken shapes.

Key Takeaways

Manual checks can miss cases and cause bugs.

Exhaustive pattern matching forces handling all cases.

This leads to safer, clearer, and more reliable code.