Lesson overview · Free interview practice

Functional Programming

Learn about pure functions, immutability, and managing side effects.

Topics in the full lesson
  • Introduction to Functional Programming
  • Pure Functions
  • Immutability
  • Side Effects
  • Higher-Order Functions
  • Functional Programming Techniques
  • Best Practices
  • Exercises

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TheoryEasy

Immutability in Practice

Question

What does immutability mean in JavaScript, and what tools does the language give you to enforce it?

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

Side Effects — What They Are and How to Corral Them

Question

What is a side effect in a function, and how do FP-style codebases keep them under control?

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

Pure Functions

Question

What is a pure function, and what makes it "pure"? Why do FP-style codebases prize purity?

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

Function Composition: `compose` and `pipe`

Question

Implement compose and pipe — variadic function composers. How do they differ, and why is pipe often preferred?

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Explain your reasoning or try an implementation before comparing answers.

TheoryHard

Currying and Partial Application

Question

What is currying, and how does it differ from partial application? Implement a generic curry and show how it enables function composition.

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Explain your reasoning or try an implementation before comparing answers.

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