Map vs forEach in JavaScript
Both of them iterate through the elements of an array. The difference here is that map
creates a new array while forEach
doesnβt. If you follow the functional programming paradigm and you want to keep data immutable then you should use map
. If you want to mutate the elements of the original array, you should use forEach
. Take the following example:
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const animals = [...];
// Mutate the elements of the original array
animals.forEach((animal, index) => animals[index] = `${animal} ποΈ`);
// Creates a new array
const newAnimals = animals.map(animal => `${animal} ποΈ`);
When using forEach
, the animals
array will also be changed. This is not the case for map
. It will create an entire new array. To reiterate:
- The callback of
forEach
mutates the original items in the array map
returns a transformed array while keeping the original intact
Note that forEach
itself does not mutate the array. However, the callback that you pass to it may do if you choose to.
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