How can I approach and align elements in the array?

Question

I already tried:

let age = arr.sort(function(a, b) {
    return b -a;
});

it was good for simple array, but it does not work. In this array:

let list = [
  [
    ['firstName', 'Joe'],
    ['age', 42],
    ['gender', 'male'],
  ],
  [
    ['firstName', 'Mary'],
    ['lastName', 'Jenkins'],
    ['age', 36],
    ['gender', 'female'],
  ],
  [
    ['lastName', 'Kim'],
    ['age', 40],
    ['gender', 'female'],
  ],
];

it's double array, and 'age' index locate is different. How can I approach the 'age' and align? I want to sort ascending.

Answer 1

You can use fromEntries to convert your array item into object and then sort. But you should consider updating the item to object to avoid this unnecessary conversion.

const list = [ [ ['firstName', 'Joe'], ['age', 42], ['gender', 'male'], ], [ ['firstName', 'Mary'], ['lastName', 'Jenkins'], ['age', 36], ['gender', 'female'], ], [ ['lastName', 'Kim'], ['age', 40], ['gender', 'female'], ], ];
list.sort((a, b) => Object.fromEntries(a).age - Object.fromEntries(b).age);

console.log(list);

Answer 2

You can do the following by finding the index of the child array where we can find age. From the example we can see that age is at index 0 and the age value is at index 1 of the sub array. You can than compare the age values.

 list = [
  [
    ['firstName', 'Joe'],
    ['age', 42],
    ['gender', 'male'],
  ],
  [
    ['firstName', 'Mary'],
    ['lastName', 'Jenkins'],
    ['age', 36],
    ['gender', 'female'],
  ],
  [
    ['lastName', 'Kim'],
    ['age', 40],
    ['gender', 'female'],
  ],
];

res = list.sort((a, b) => {
  ageIndexA = a.findIndex(item => item[0] ==='age');
  ageIndexB = b.findIndex(item => item[0] === 'age');
  return a[ageIndexA][1] - b[ageIndexB][1];
});

console.log(res);

Answer 3

The following should work:

let list = [
  [
    ['firstName', 'Joe'],
    ['age', 42],
    ['gender', 'male'],
  ],
  [
    ['firstName', 'Mary'],
    ['lastName', 'Jenkins'],
    ['age', 36],
    ['gender', 'female'],
  ],
  [
    ['lastName', 'Kim'],
    ['age', 40],
    ['gender', 'female'],
  ],
];
const compareFunction = (a,b) => {
  return a.age - b.age;
}
const sortList = (arr) => {
  const objectList = arr.map(e => Object.fromEntries(e));
  return objectList.sort(compareFunction);
}
console.log('sorted:', sortList(list));

Answer 4

The following will sort your array according to ascending age:

let list = [
  [
    ['firstName', 'Joe'],
    ['age', 42],
    ['gender', 'male'],
  ],
  [
    ['firstName', 'Mary'],
    ['lastName', 'Jenkins'],
    ['age', 36],
    ['gender', 'female'],
  ],
  [
    ['lastName', 'Kim'],
    ['age', 40],
    ['gender', 'female'],
  ],
];
let age = list.sort(function(a, b) {
    return a.filter(aa=>aa[0]=="age")[0][1] 
          -b.filter(bb=>bb[0]=="age")[0][1];})
    
console.log(age)

// this is a better approach:
let listo=list.map(e=>e.reduce((a,[k,v])=>(a[k]=v,a), {}));
console.log(listo.sort((a,b)=>a.age-b.age))

However, it would be better to store your data in a different format:. My second part generates such a format in listo. The sorting function is then trivial again ((a,b)=>a.age-b.age):

[
  {
    "firstName": "Mary",
    "lastName": "Jenkins",
    "age": 36,
    "gender": "female"
  },
  {
    "lastName": "Kim",
    "age": 40,
    "gender": "female"
  },
  {
    "firstName": "Joe",
    "age": 42,
    "gender": "male"
  }
]
``´