Arranging a map by its keys results in a sorted Map object with the initial key located at the end of

Question

Arranging a map by its keys results in a sorted Map object with the initial key located at the end of

I have a function that creates a Map object from two arrays and then attempts to sort the map by key. Despite following the sort method as outlined in Mozilla Docs, the sorting is not working as expected; it places the first key at the last index when using the mapSort object.

const sortMapByKey = () => {
  const keyArray = [4, 6, 16, 18, 2]
  const valueArray = [103, 123, 4444, 99, 2000]

  const buildMap = (keys, values) => {
      const map = new Map();
      for(let i = 0; i < keys.length; i++){
        map.set(keys[i], values[i]);
      };
      const mapSort = new Map([...map.entries()].sort(function(a, b) {
        return a - b;
      }));
      return mapSort
    };  
    
    return buildMap(keyArray, valueArray)
}

The current output:

Map { 4 => '103', 6 => '123', 16 => '4444', 18 => '99', 2 => '2000' }

The desired output:

Map {  2 => '2000', 4 => '103', 6 => '123', 16 => '4444', 18 => '99' }

I'm puzzled about what might be going wrong with my sort implementation. Any insights?

javascript arrays sorting

Answer 1

Answer №1

In this scenario, the entries are represented as key-value pairs, for example: [1, 103]. The code snippet return a - b attempts to subtract two arrays containing such entries, which is not meaningful. Instead, it is necessary to extract the key from each entry pair before performing any operations.

const mapSort = new Map([...map.entries()].sort(function(entryA, entryB) {
  return entryA[0] - entryB[0];
}));

const keyArray = [4, 6, 16, 18, 2]
const valueArray = [103, 123, 4444, 2000]

const buildMap = (keys, values) => {
  const map = new Map();
  let objectArray = []
  for (let i = 0; i < keys.length; i++) {
    map.set(keys[i], values[i]);
  };
  const mapSort = new Map([...map.entries()].sort(function(entryA, entryB) {
    return entryA[0] - entryB[0];
  }));
  return mapSort
};

console.log(buildMap(keyArray, valueArray));

Alternatively, you can utilize destructuring like so:

const mapSort = new Map(
  [...map.entries()]
    .sort(([a], [b]) => a - b)
);

const keyArray = [4, 6, 16, 18, 2]
const valueArray = [103, 123, 4444, 2000]

const buildMap = (keys, values) => {
  const map = new Map();
  let objectArray = []
  for (let i = 0; i < keys.length; i++) {
    map.set(keys[i], values[i]);
  };
  const mapSort = new Map(
    [...map.entries()]
      .sort(([a], [b]) => a - b)
  );
  return mapSort
};

console.log(buildMap(keyArray, valueArray));

Answer 2

In this scenario, the entries are represented as key-value pairs, for example: [1, 103]. The code snippet return a - b attempts to subtract two arrays containing such entries, which is not meaningful. Instead, it is necessary to extract the key from each entry pair before performing any operations.

const mapSort = new Map([...map.entries()].sort(function(entryA, entryB) {
  return entryA[0] - entryB[0];
}));

const keyArray = [4, 6, 16, 18, 2]
const valueArray = [103, 123, 4444, 2000]

const buildMap = (keys, values) => {
  const map = new Map();
  let objectArray = []
  for (let i = 0; i < keys.length; i++) {
    map.set(keys[i], values[i]);
  };
  const mapSort = new Map([...map.entries()].sort(function(entryA, entryB) {
    return entryA[0] - entryB[0];
  }));
  return mapSort
};

console.log(buildMap(keyArray, valueArray));

Alternatively, you can utilize destructuring like so:

const mapSort = new Map(
  [...map.entries()]
    .sort(([a], [b]) => a - b)
);

const keyArray = [4, 6, 16, 18, 2]
const valueArray = [103, 123, 4444, 2000]

const buildMap = (keys, values) => {
  const map = new Map();
  let objectArray = []
  for (let i = 0; i < keys.length; i++) {
    map.set(keys[i], values[i]);
  };
  const mapSort = new Map(
    [...map.entries()]
      .sort(([a], [b]) => a - b)
  );
  return mapSort
};

console.log(buildMap(keyArray, valueArray));

Arranging a map by its keys results in a sorted Map object with the initial key located at the end of

Answer №1

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