Why is this returning false? (Simple code)

Question

This is a simple code designed to tell me if one array has an array equal to it in an array consisting of arrays. So the following function should be returning true but it returns false.


var TransferR =[0,8,16,24,32,40,48,56]



var rookV =[
[0,8,16,24,32,40,48,56],
[1,9,17,25,33,41,49,57],
[2,10,18,26,34,42,50,58],
[3,11,19,27,35,43,51,59],
[4,12,20,28,36,44,52,60],
[5,13,21,29,37,45,53,61],
[6,14,22,30,38,46,54,62],
[7,15,23,31,39,47,55,63],
]
   

const match = rookV.some(memb=> memb === TransferR)
console.log(match)

[Duplicate](//google.com/search?q=site%3Astackoverflow.com+js+array+comparison+always+false) of [How to compare arrays in JavaScript?](/q/7837456/4642212). — Sebastian Simon, Jun 03 '21 at 19:07

score 1 · Answer 1 · edited Jun 03 '21 at 19:21

1

You can't compare arrays with ===, which compares the references. Compare array length and then each value.
For example:

const match = rookV.some(memb=> {
  memb.length === TransferR.length && memb.every(el => TransferR.includes(el))
});

This code will first check that there is a match in the length (so it will skip arrays that are uncomparable), and than will check that every element of memb is included in the TransferR array, returning true or false.

edited Jun 03 '21 at 19:21

ISAE

519
4
12

answered Jun 03 '21 at 19:09

yanjunk

336
1
5

Thanks. but what do you mean exactly? If I know the arrays will be equal in length, how can I check to see if both have the same contents? – Deerman1989 Jun 03 '21 at 19:17
See the edit (manually checks each element). – yanjunk Jun 03 '21 at 19:22

score 0 · Answer 2 · answered Jun 03 '21 at 19:17

how about stringify it?

var TransferR = [0, 8, 16, 24, 32, 40, 48, 56]



var rookV = [
  [0, 8, 16, 24, 32, 40, 48, 56],
  [1, 9, 17, 25, 33, 41, 49, 57],
  [2, 10, 18, 26, 34, 42, 50, 58],
  [3, 11, 19, 27, 35, 43, 51, 59],
  [4, 12, 20, 28, 36, 44, 52, 60],
  [5, 13, 21, 29, 37, 45, 53, 61],
  [6, 14, 22, 30, 38, 46, 54, 62],
  [7, 15, 23, 31, 39, 47, 55, 63],
]


const match = rookV.some(
  memb => JSON.stringify(memb) === JSON.stringify(TransferR))
console.log(match)

Why is this returning false? (Simple code)

2 Answers2