javascript map sorting by value

Question

javascript map sorting by value

I am working with an object that has a many-to-one mapping setup:

{
  'a' : 'one',
  'b' : 'two',
  'c' : 'one',
  'd' : 'two'
}

My goal is to transform this object into the following structure:

{
  'one' : ['a' , 'c'],
  'two' : ['b' , 'd']
}

What is the most efficient way to achieve this transformation in javascript? (We are open to using underscore libraries if it simplifies the process) Please note that the objects provided above are simplified examples of the actual data we are working with.

javascript arrays sorting dictionary underscore.js

Answer 1

Answer №1

let information = {
  'x' : 'first',
  'y' : 'second',
  'z' : 'first',
  'w' : 'second'
}

let output = {};

for(let property in information) {
    let value = information[property];
    if(!output[value]) output[value] = [];

    output[value].push(property);
}

console.log(output);

Answer 2

let information = {
  'x' : 'first',
  'y' : 'second',
  'z' : 'first',
  'w' : 'second'
}

let output = {};

for(let property in information) {
    let value = information[property];
    if(!output[value]) output[value] = [];

    output[value].push(property);
}

console.log(output);

Answer 3

Answer №2

If you want to achieve this task, you can utilize the Object.keys() method along with reduce

var data = {'a': 'one','b': 'two','c': 'one','d': 'two'}

var result = Object.keys(data).reduce((res, e) => {
  res[data[e]] = (res[data[e]] || []).concat(e);
  return res;
}, {});

console.log(result)

An alternative approach is to use forEach method and add elements to the newly created object

var data = {'a': 'one','b': 'two','c': 'one','d': 'two'}, r = {}

Object.keys(data).forEach(e => {r[data[e]] = (r[data[e]] || []).concat(e)});
console.log(r)

Answer 4

If you want to achieve this task, you can utilize the Object.keys() method along with reduce

var data = {'a': 'one','b': 'two','c': 'one','d': 'two'}

var result = Object.keys(data).reduce((res, e) => {
  res[data[e]] = (res[data[e]] || []).concat(e);
  return res;
}, {});

console.log(result)

An alternative approach is to use forEach method and add elements to the newly created object

var data = {'a': 'one','b': 'two','c': 'one','d': 'two'}, r = {}

Object.keys(data).forEach(e => {r[data[e]] = (r[data[e]] || []).concat(e)});
console.log(r)

Answer 5

Answer №3

Here is my solution to the problem at hand. It may not be as intricate as Nenad's, but it gets the job done.

let data = {
  'x' : 'foo',
  'y' : 'bar',
  'z' : 'foo',
  'w' : 'bar'
};

let output = {};

for (let key in data) {
  if (data[key] in output) {
    output[data[key]].push(key);
  } else {
    output[data[key]] = [key];
  }
}

console.log(output);

Answer 6

Here is my solution to the problem at hand. It may not be as intricate as Nenad's, but it gets the job done.

let data = {
  'x' : 'foo',
  'y' : 'bar',
  'z' : 'foo',
  'w' : 'bar'
};

let output = {};

for (let key in data) {
  if (data[key] in output) {
    output[data[key]].push(key);
  } else {
    output[data[key]] = [key];
  }
}

console.log(output);

Answer 7

Answer №4

a concise solution

var obj = {
  'apple' : 'red',
  'banana' : 'yellow',
  'cherry' : 'red',
  'date' : 'brown'
},

result = Object.keys(obj).reduce((prev, current) => {!!prev[obj[current]] ? prev[obj[current]].push(current) : prev[obj[current]] = [current]; return prev},{})

document.write("<pre>" + JSON.stringify(result) + "</pre>");

Answer 8

a concise solution

var obj = {
  'apple' : 'red',
  'banana' : 'yellow',
  'cherry' : 'red',
  'date' : 'brown'
},

result = Object.keys(obj).reduce((prev, current) => {!!prev[obj[current]] ? prev[obj[current]].push(current) : prev[obj[current]] = [current]; return prev},{})

document.write("<pre>" + JSON.stringify(result) + "</pre>");

javascript map sorting by value

Answer №1

Answer №2

Answer №3

Answer №4

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