JS sorts by a key value of the object

ask how the following array is sorted by id.

let data = [
  {
    a:12,
    b:[
      {id: 3}
    ]
  },
  {
    a:12,
    b:[
      {id: 1}
    ]
  },
  {
    a:12,
    b:[
      {id: 2}
    ]
  },
];
Mar.05,2022

data.sort(function(a,b){
  return a.b[0].id-b.b[0].id>0?-1:1;
})

data.sort((a, b) => {
    return a.b[0].id - b.b[0].id > 0 ? 1 : -1
})
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