array.map is not a function even though I have it typed correctly

Question

I am wondering why I'm getting this error message? But array.map is correct in how I'm stating it?

/home/ccuser/workspace/credit-card-checker/main.js:40 newArr = array.map((element, index) => index % 2 === 1? element * 2: element); ^

TypeError: array.map is not a function at validateCred

 const valid1 = [4, 5, 3, 9, 6, 7, 7, 9, 0, 8, 0, 1, 6, 8, 0, 8]; const validateCred = (array) => { let newArr = []; let newestArr = []; let reducedResult = 0; const reducer = (previousValue, currentValue) => previousValue + currentValue; if (array.length % 2 === 0) { newArr = array.map((element, index) => index % 2 === 0? element * 2: element); } else { newArr = array.map((element, index) => index % 2 === 1? element * 2: element); } newestArr = newArr.map((element) => element > 9? element - 9: element); let sum = newestArr.reduce((prev, curr) => prev += curr); return sum % 10 === 0 }; const findInvalidCards = (nestedArray) => { let invalidArray = []; invalidArray = nestedArray.forEach((element) => validateCred(element) === false); return invalidArray; }; findInvalidCards(valid1);

Answer 1

valid1 is supposed to be an array of arrays, so here I just wrap another set of square brackets.

Also, forEach always returns undefined, so I changed it to use map instead.

 const valid1 = [[4, 5, 3, 9, 6, 7, 7, 9, 0, 8, 0, 1, 6, 8, 0, 8]]; const validateCred = (array) => { let newArr = []; let newestArr = []; let reducedResult = 0; const reducer = (previousValue, currentValue) => previousValue + currentValue; if (array.length % 2 === 0) { newArr = array.map((element, index) => index % 2 === 0? element * 2: element); } else { newArr = array.map((element, index) => index % 2 === 1? element * 2: element); } newestArr = newArr.map((element) => element > 9? element - 9: element); let sum = newestArr.reduce((prev, curr) => prev += curr); return sum % 10 === 0 }; const findInvalidCards = (nestedArray) => { let invalidArray = []; invalidArray = nestedArray.map((element) => ({cardNumber: element.join(""), isValid: validateCred(element)})); return invalidArray; }; console.log(findInvalidCards(valid1));