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JavaScript Asynchronous Programming with JavaScript Asynchronous JavaScript with Callbacks Implement a Callback

Posted by Mohamed El-Damarawy
Mohamed El-Damarawy
11,294 Points

map vs forEach

Why did we loop with map and not forEach? Does it make any difference in the context of this exercise?

I think my issue here is understanding the difference between map and forEach

1 Answer

Steven Parker
Steven Parker
229,732 Points
Steven Parker
Steven Parker
229,732 Points

The difference between forEach and map is the handling of return values. The map method builds a new array made of the return values from the callback and then returns that array, while forEach ignores any return value from the callback and its own return is undefined.

So use map when your callback returns a value, and you will use an array made up of those values.

David Adams
.a{fill-rule:evenodd;}techdegree seal-36
David Adams
Full Stack JavaScript Techdegree Graduate 18,557 Points

That makes sense! In this case, it looks like forEach() works also. Is there any reason .map() is preferable in this particular case, given (at least so far), the returned array is not being used?

Steven Parker
Steven Parker
229,732 Points
Steven Parker
Steven Parker
229,732 Points

When the return value from "map" isn't used, there's no functional difference from "forEach".