how to get the first item in nested, filtered array in javascirpt

January 28, 2022

I’ve got an array:

const aContracts = [[ '0x8ae127d224094cb1b27e1b28a472e588cbcc7620', 0 ],
  [ '0xcbf4ab00b6aa19b4d5d29c7c3508b393a1c01fe3', 0 ],
  [ '0x03cd191f589d12b0582a99808cf19851e468e6b5', 0 ],
  [ '0x0b3f868e0be5597d5db7feb59e1cadbb0fdda50a', 1 ]]

And I’m trying to filter using the second item in each sub-array. So I used:

const aGoodContracts = aContracts.filter(contracts => contracts[1]===1);

And I get:

[["0x0b3f868e0be5597d5db7feb59e1cadbb0fdda50a", 1]]

However, I want [EDIT I want an array of all the "good" contracts]:

"0x0b3f868e0be5597d5db7feb59e1cadbb0fdda50a"

So I tried a solution I found here:
const aGoodContracts = aContracts.map(k => k.filter(contracts => contracts[1]===1));

But I get:

[[], [], [], []]

What am I missing?

>Solution :

Just map() your result to pick out the first element in the array. This will leave you with an array, and if you just want the first value (like your expected output) grab the zero index element.

const aContracts = [[ '0x8ae127d224094cb1b27e1b28a472e588cbcc7620', 0 ],
  [ '0xcbf4ab00b6aa19b4d5d29c7c3508b393a1c01fe3', 0 ],
  [ '0x03cd191f589d12b0582a99808cf19851e468e6b5', 0 ],
  [ '0x0b3f868e0be5597d5db7feb59e1cadbb0fdda50a', 1 ]]

const aGoodContracts = aContracts.filter(contracts => contracts[1]===1).map(c => c[0]);
console.log(aGoodContracts);
console.log(aGoodContracts[0]);