Sep 17, 2026 · 8 min · 7 segments
In your previous activities you learned how to loop over arrays with 'for', 'for... of' and 'while'. These classic loops work perfectly, but modern JavaScript offers dedicated array methods that make…
In your previous activities you learned how to loop over arrays with for, for, of and while.
These classic loops work perfectly, but modern JavaScript offers dedicated array methods that make your code shorter, more readable and easier to reason about.
In this chapter we introduce three of the most important ones, map, filter and reduce.
They belong to a family called higher order functions, which simply means functions that take another function as an argument.
Understanding them is a decisive step toward writing professional, clean and maintainable code.
Why use these methods instead of loops? They express intent clearly.
They do not modify the original array.
They are non-destructive, which reduces bugs.
They chain together elegantly, letting you build data processing pipelines.
A callback is a function you pass to another function so it can be called later.
With map, filter and reduce, the callback is executed once for every element of the array.
The callback commonly receives up to three arguments.
The current element, its index, and the whole array.
In most everyday cases you only use the first argument.
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In your previous activities you learned how to loop over arrays with for, for, of and while.
These classic loops work perfectly, but modern JavaScript offers dedicated array methods that make your code shorter, more readable and easier to reason about.
In this chapter we introduce three of the most important ones, map, filter and reduce.
They belong to a family called higher order functions, which simply means functions that take another function as an argument.
Understanding them is a decisive step toward writing professional, clean and maintainable code.
Why use these methods instead of loops? They express intent clearly.
They do not modify the original array.
They are non-destructive, which reduces bugs.
They chain together elegantly, letting you build data processing pipelines.
A callback is a function you pass to another function so it can be called later.
With map, filter and reduce, the callback is executed once for every element of the array.
The callback commonly receives up to three arguments.
The current element, its index, and the whole array.
In most everyday cases you only use the first argument.