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Intro

• Dynamic languages will benefit from different design patterns from static or compiled languages
• Why care about design patterns? Knowing the name for a concept gives us a common language to discuss them with.

An opinionated list of good design patterns

...Some of which come from the Design Patterns book by the Gang of Four.

Feature Flags

• Not a “traditional” design pattern
• Enable fast rollbacks and gradual releases

Singleton

• Guarantee a given class only has one instance while making that instance globally available
• Enable access to a shared resource (file, DB, web socket, etc.)

Decorator

• Attach instrumentation (such as tracing) to another function
• TS has first-class decorators
• TC39 has stage 3 proposal for decorators
• Multiple types: method decorator, class decorator

Proxy

• Enables controlling access to an object
• Built-in Proxy in JS: new Proxy(obj, handler) where handler intercepts and redefines what methods (such as obj.get should return)
• Mozilla docs

Fluent Interface

• An object-oriented API that relies on method chaining
• Increase code legibility and composability with a domain-specific language

Ending thoughts

Consider if you’re more of a just-in-time learner or a just-in-case learner, and give the other type a try sometime!