How to sort object of arrays by nested property in JavaScript-CodePudding

I have the following object:

const obj = {
  A: [{
    capacity: 100
  }, {
    capacity: 100
  }, {
    capacity: 100
  }],
  B: [{
    capacity: 500
  }, {
    capacity: 500
  }, {
    capacity: 500
  }],
  C: [{
    capacity: 300
  }, {
    capacity: 300
  }, {
    capacity: 300
  }]
}

I need to transform to an object with the same shape but with the keys sorted by capacity. To note, the capacity of each object in the arrays (A, B, C) is always the same within the same object. So we can take the first occurrence for example

Expected result:

const obj = {
  A: [{
    capacity: 100
  }, {
    capacity: 100
  }, {
    capacity: 100
  }],
  C: [{
    capacity: 300
  }, {
    capacity: 300
  }, {
    capacity: 300
  }],
  B: [{
    capacity: 500
  }, {
    capacity: 500
  }, {
    capacity: 500
  }]
}

None of my approaches worked out. An example:

const sortByPosition = obj => {
   const order = [], res = {};
   Object.keys(obj).forEach(key => {
      return order[obj[key][1]['capacity'] - 1] = key;
   });
   order.forEach(key => {
      res[key] = obj[key];
   });
   return res;
}

console.log(sortByPosition(obj));

Here's a fiddle

CodePudding user response：

There are several methods to solve your problem, here is the best understandable one:

const sortByPosition = obj => {
  let sortable = [];
  let objSorted = {};
  
  for (let key in obj) {
      sortable.push([key, obj[key]]);
  }

  sortable.sort(function(a, b) {
      return a[1][0].capacity - b[1][0].capacity;
  });
  
  
  sortable.forEach(function(item){
      objSorted[item[0]] = item[1]
  })
  
  return objSorted;
}

console.log(sortByPosition(obj));
console.log(Object.keys(sortByPosition(obj)));
console.log(Object.keys(obj));

I printed 3 logs in my code. In the result of first log, it seems to be no change. But from the 2nd and 3rd logs, we can see that the result is correct. Those logs are follows:

["A", "C", "B"]
["A", "B", "C"]

CodePudding user response：

const obj = {
  A: [ { capacity: 100 }, { capacity: 100 }, { capacity: 100 } ],
  B: [ { capacity: 500 }, { capacity: 500 }, { capacity: 500 } ],
  C: [ { capacity: 300 }, { capacity: 300 }, { capacity: 300 } ]
};

console.log(Object.fromEntries(Object.entries(obj)
  .sort(([i,a],[j,b])=>a[0].capacity-b[0].capacity)));