Sorting nested Array inside Array using sort

Question

I want to sort nested array (array inside an array) i.e My array looks like this

const input = [[3,9],[7,12],[3,8],[6,8],[9,10],[2,9],[0,9],[3,9],[0,6],[2,8]]

To do that I wrote this logic

const input = [[3,9],[7,12],[3,8],[6,8],[9,10],[2,9],[0,9],[3,9],[0,6],[2,8]]
    
    
     function sort (a,b) {
      if (a[0] < b[0]) return -1
      if (a[0] > b[0]) return 1
      if (a[0] === b[0]) {
        if (a.length > 1 && b.length > 1) {
          return sort(a.slice(0, 1), b.slice(0,1))
        }
        else return 0
      } 
    }

  console.log(input.sort((a,b) => {
    return sort(a,b)
  }))

but this is giving first element as [0,9] instead of [0, 6] and [2, 9] instead of [2,8] so on.

What I want is

Compare first element, if first element is equal, compare second ending elemennt

So [0, 6] should be before [0,9]...

to fix the code you wrote, you'd need return sort(a.slice(1, 2), b.slice(1,2)) — Jaromanda X
– Jaromanda X, Commented Oct 12, 2020 at 1:32

CertainPerformance · Accepted Answer · 2020-10-12 01:37:33Z

4

All you need for the callback is a[0] - b[0] || a[1] - b[1]:

const input = [[3,9],[7,12],[3,8],[6,8],[9,10],[2,9],[0,9],[3,9],[0,6],[2,8]]
console.log(input.sort((a,b) => a[0] - b[0] || a[1] - b[1]))

If the array is of arbitrary length, then you do need a separate named function:

const sort = (a, b) => a[0] - b[0] || sort(a.slice(1), b.slice(1));

const input = [[3,9],[7,12],[3,8],[6,8],[9,10],[2,9],[0,9],[3,9],[0,6],[2,8]]
console.log(input.sort((a,b) => a[0] - b[0] || a[1] - b[1]))

edited Oct 12, 2020 at 1:37

answered Oct 12, 2020 at 1:31

CertainPerformance

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2 Comments

Diza Moa Over a year ago

Can you please explain this line of code a[0] - b[0] || a[1] - b[1] in input.sort((a,b) => a[0] - b[0] || a[1] - b[1])

CertainPerformance Over a year ago

It will return the difference if the first items in the arrays are different. Otherwise, if they're the same, it'll return the difference between the second items in the arrays.

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