Mixin Pattern

A mixin is an object that we can use in order to add reusable functionality to another object or class, without using inheritance. We can't use mixins on their own: their sole purpose is to add functionality to objects or classes without inheritance.

Let's say that for our application, we need to create multiple dogs. However, the basic dog that we create doesn't have any properties but a name property.

When to Use

• Use this when you need to add reusable functionality to multiple classes without creating an inheritance chain
• This is helpful when you want to compose behavior from multiple sources

When NOT to Use

• When composition via hooks (React) or composables (Vue) achieves the same result with better traceability
• When prototype pollution is a risk — mixins modify shared prototypes and can cause naming collisions
• When the added functionality is simple enough that a utility function or module import suffices

Instructions