.find within .map() returns undefined - JavaScript ES6 [duplicate]

Question

return valuesArray.map((objValue) => {
         Dataset.find(dataObj => dataObj.value === objValue)
});

it returns undefined. However, if I use forEach and push values into an new array, it works.

you aren't returning anything. either use return or drop the curlies — Daniel A. White
– Daniel A. White, Commented May 18, 2018 at 1:45
@CodeBreaker This behavior is strange.Even I ma doing same and I am getting undefined, even I have returned properly. @Daniel A. White can you help here ? resources.map((resource) => members.find((member) => member.identifier === resource)) — Vipulw
– Vipulw, Commented Oct 27, 2020 at 8:06
@Vipulw please post a new question with a minimal reproducible example — Daniel A. White
– Daniel A. White, Commented Oct 27, 2020 at 14:07

Praveen Kumar · Accepted Answer · 2018-05-18 05:37:06Z

7

You can also check with filter to check for undefined.

return valuesArray.map((objValue) => {
        return Dataset.find(dataObj => dataObj.value === objValue)
}).filter(y => y != undefined);

So it will not return the undefined from the valuesArray also.

answered May 18, 2018 at 5:37

Praveen Kumar

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Comments

Isaac · Accepted Answer · 2018-05-18 01:56:45Z

1

You're missing a return value.

With anonymous functions, if you encase the function in curly braces, you have to explicitly return a value.

To answer your question, here are 2 methods that will work:

return valuesArray.map((objValue) => {
         return Dataset.find(dataObj => dataObj.value === objValue)
});

or

return valuesArray.map((objValue) => Dataset.find(dataObj => dataObj.value === objValue));

answered May 18, 2018 at 1:46

Isaac

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Consider adding an explanation as to why the OP's code didn't work and what you've changed