Fix: Array.prototype.map() Expects a Return Value From Arrow Function

Make sure the filter function has a return statement

2 min. read

Published onDecember 20, 2023

published onDecember 20, 2023

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Key notes

You may get theArray.prototype.map() expects a return value from arrow functionerror when using theArray.map() arrowfunction.

The error appears when the map function returns nothing or if the filter method is used wrongly. Besides, users sometimes mistakenly set up forArray.forEach()instead ofArray.map(), which triggers the error.

How do I fix Array.prototype.map() expects a return value from arrow function?

Before we start with the slightly complex solutions, try these quick ones:

1. Use the Array.prototype.forEach() function

If a return value is not required from the function, and the array created byArray.prototype.map()is not used, then go with theArray.prototype.forEach()function.

The latter doesn’t return any special value and is the best choice in such cases. To learn more aboutArray.prototype.forEach(),check theMozilla developer document.

2. Replace {} with ()

Using{}in the function will create an arrow block that requires an explicit return statement. If that’s not the case with your code, replace it with().

Now, you will have an implicit return and theArray.prototype.map() expects a return value from arrow functionerror will be fixed.

3. Return null

Another approach is to return a null value if the provided conditions don’t match. To do that, add the following toward the end, right before the closing parenthesis:return null;

4. Use Array.prototype.filter() instead

If it requires filtering, you should consider usingArray.prototype.filter()instead ofArray.prototype.map(). This will create a copy of the elements that pass the requirements set by the function.

To read more aboutArray.prototype.filter(), check theMozilla developer document.

These are all the ways to fix theArray.prototype.map() expects a return value from arrow functionerror. Remember, you don’t necessarily have to use themap()function each time. Given the situation and whether a return value is required, switch tofilter()andforEach().

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For any queries or to share how you fixed the error, drop a comment below.

Fix: Array.prototype.map() Expects a Return Value From Arrow Function#

How do I fix Array.prototype.map() expects a return value from arrow function?#

1. Use the Array.prototype.forEach() function#

2. Replace {} with ()#

3. Return null#

4. Use Array.prototype.filter() instead#