How to remove Comma from output element after mapping an Array in React js

I want the output like: Custom(F,T,S)

But output comes like,

My code:

‘Custom’ + (${data.state?.days?.map((item) => item.day ? item.day : '')})

Thanks………..

>Solution :

TL&DR :

'Custom' + (${data.state?.days?.filter((item) => !!item.day).map((item) => item.day)})

Array.map always transform all the entries of an array.
In your case, you have some some item that don’t have a "day".
So, you create a new array with empty elements

First, you have to filter your array :

data.state?.days?.filter((item) => !!item.day)

Then map through it

data.state?.days?.filter((item) => !!item.day).map((item) => item.day)