JavaScript: Functions, Scope & Arrow Functions

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About Course

Functions are the building blocks of JavaScript. Learn the different ways to define them, how parameters, default values and return work, how scope and closures decide which variables a function can see, and when arrow functions behave differently from ordinary functions.

Tutwoo is independent and is not affiliated with or endorsed by Mozilla. Examples are for learning; follow your organisation’s coding standards.

© 2026 Tutwoo UK Limited. This course was created in-house by Tutwoo and is our original work. It is for your own learning only: please do not copy, share, record or resell it.

What Will You Learn?

  • Write function declarations, function expressions and arrow functions
  • Use parameters, default values, rest parameters and return values correctly
  • Explain block scope with let and const, and how closures work
  • Know the limitations of arrow functions, including this and new

Course Content

Course Lessons

  • Defining and calling functions
  • Parameters, defaults and return values
  • Scope and closures
  • Arrow functions and their limitations

Sources & Further Reading
The official guidance this course is based on.

Final Assessment

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