![]() Shout out to reduce for when you want to get an accumulate value by looping.JavaScript is among the most-used programming languages. ![]() To achieve the same result using forEach is more clunky. The forEach loop always returns undefined. And it’s not the best idea anyways considering the popular practice of coding with immutability.įor transformations you can use map and filter which both returns a new array. The forEach loop works on a copy, so even if you try to alter the elements, the array remains unchanged. One example being the “backwards for loop” where the conditional does not need to include an array.length check. Also there are performance improvements you can make to both for and forEach. ![]() It’s hard to say the exact numbers here since it varies per platform but I have seen performance differences from 2x up to 20x. That means lowered cost compared to the forEach. The for loop uses an initializing statement and a conditional that is evaluated at every iteration. This additional scope leads to slower speeds compared to the for loop. In the forEach loop, we are invoking the callback function on every iteration. Instead go for array methods ‘find’, ‘findIndex’ or a for loop which you can terminate. As an example, searching for an element is therefore not a good use case for a forEach loop. Because of this limitation you should expect a runtime matching linearly to the size of the looped array. In a forEach loop the only way to terminate the loop is to throw an exception. Short-circuiting means terminating or skipping an iteration of the loop. ![]() If you want to short circuit or break out of the loop ![]() Let’s get into the situations where the forEach loop is just a bad fit. Personally I think that the “for of” loop is even more readable. Some developers like the readability of a forEach loop and that can be a valid point since it’s a subjective matter. I have yet to discovered a situation where forEach is the only reasonable solution and I find myself using it less and less. The forEach loop is part of most JS developers toolbelt. ![]()
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