The forEach and map functions are two essential methods for iterating and transforming arrays in JavaScript. In this chapter, you will learn how to use these functions with practical examples and common use cases, including some details on performance and best practices.

forEach

The forEach method executes a function on each element of an array. It is useful for performing actions on the elements of an array but does not return a new array.

Example of forEach

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Performance Considerations

Although forEach is simple and easy to use, it may not be the best choice if your goal is to transform an array. This is because forEach does not return a new array, and if you need to mutate the original array, other techniques like map or reduce might be more suitable.

map

The map method creates a new array from the results of applying a function to each element of the original array. It is perfect when you want to transform data without mutating the original array.

Example of map

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Using map on Arrays of Objects

The map method is particularly useful when working with arrays of objects, as it allows you to easily transform values within those objects.

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Conclusion

The forEach and map functions are powerful tools for iterating and transforming arrays. While forEach is ideal for executing actions on the elements, map is the best choice when you want to transform an array without modifying the original.