changing from array list to an object javascript

Question

I have a problem with my code as when I increase the number of elements inside the array it runs only the last added 3 elements only not the full list I don't know what's wrong in my code. please help!

var array = [
  ['make', 'Ford'],
  ['model', 'Mustang'],
  ['year', '1964'],
  ['make', 'Honda'],
  ['model', 'CRV'],
  ['year', '2000']
];

function fromListToObject(array) {
  var obj = Object.create(null); // empty container for my object
  for (var i = 0; i < array.length; i++) { //declare the 1st array loop
    var arr1 = array[i]; //decleare the nested array
    obj[arr1[0]] = arr1[1]; //1st item = 2nd item in the nested array
  }
  return obj;
}

var result = fromListToObject(array);
console.log(result);

Why you are using obj[arr1[0]] always?. Isn't it about your loop step increment element i? — Murat Seker
– Murat Seker, Commented Jul 13, 2017 at 10:25
It's because objects can have only one value for a given property, unless you put value into an array. What result do you expect? Should it be: {make: ["Ford", "Mustang"], model: ["Mustang", "CRV"], year: ["1964", "2000"]} or [{ make: 'Ford', model: 'Mustang', year: '1964' }, { make: 'Honda', model: 'CRV', year: '2000' }]? — Lukasz Wiktor
– Lukasz Wiktor, Commented Jul 13, 2017 at 10:30
{ make: 'Ford', model: 'Mustang', year: '1964' }, { make: 'Honda', model: 'CRV', year: '2000' } — Salma Elshahawy
– Salma Elshahawy, Commented Jul 13, 2017 at 10:32

baao · Accepted Answer · 2017-07-13 10:44:56Z

1

You have to get the data into an array of objects. I'd chunk the original array into pieces of the then keys size, then handle those chunks and create individual objects for them. Note that below will fail if the original array contains chunks that are not equal (keys missing, e.g.), so you will need to add a check for that or be really sure that the original array is always correct:

let array = [
  ['make', 'Ford'],
  ['model', 'Mustang'],
  ['year', '1964'],
  ['make', 'Honda'],
  ['model', 'CRV'],
  ['year', '2000']
];

function toArrOfObj(array) {
  let keys = [...new Map(array).keys()];
  let i, j, res = [], chunk = keys.length;
  for (i = 0, j = array.length; i < j; i += chunk) {
    let tmp = array.slice(i, i + chunk);
    let obj = {};
    for (let [k, v] of tmp) {
      obj[k] = v;
    }
    res.push(obj);
  }
  return res;
}

console.log(toArrOfObj(array));

answered Jul 13, 2017 at 10:44

baao

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1 Comment

Lukasz Wiktor Over a year ago

The only answer that works correctly when the input array has for example 5 elements or in general a number of elements not divisible by 3.

H77 · Accepted Answer · 2017-07-13 12:57:54Z

1

Does this give you the output you're looking for?

var array = [
  ['make', 'Ford'],
  ['model', 'Mustang'],
  ['year', '1964'],
  ['make', 'Honda'],
  ['model', 'CRV'],
  ['year', '2000']
];

function fromListToObject(data) {
  var cars = [];
  for (var i = 0; i < data.length; i++) {
    var car = {};
    car[data[i][0]] = data[i++][1];
    car[data[i][0]] = data[i++][1];
    car[data[i][0]] = data[i][1];
    cars.push(car);
  }
  return cars;
}

var result = fromListToObject(array);
console.log(result);

Update: Version 2

var array = [
  ['make', 'Ford'],
  ['model', 'Mustang'],
  ['year', '1964'],
  ['make', 'Honda'],
  ['model', 'CRV'],
  ['year', '2000']
];

function fromListToObject(data) {
  var cars = [];

  var car = {};
  data.forEach(function(item) {
    if (item.length < 2)
      return;

    var key = item[0];

    // the car already has the key, so this must be new
    // add the car to the list and create a new one.
    if (car.hasOwnProperty(key)) {
      cars.push(car);
      car = {};
    }

    car[key] = item[1];
  });

  // add the last car in
  cars.push(car);
  return cars;
}

var result = fromListToObject(array);
console.log(result);

edited Jul 13, 2017 at 12:57

answered Jul 13, 2017 at 10:35

H77

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3 Comments

Lukasz Wiktor Over a year ago

Have you tried what happens when the input array has 5 elements?

H77 Over a year ago

@LukaszWiktor it was supposed to be basic code with no error handling, but I've added a new version that should handle such scenarios.

Lukasz Wiktor Over a year ago

Sure, I've already upvoted your first version because it was quite elegant. The second version is even better and works for corner cases.

Hassan Imam · Accepted Answer · 2017-07-13 10:43:41Z

0

var array = [['make', 'Ford'], ['model', 'Mustang'], ['year', '1964'],['make', 'Honda'], ['model', 'CRV'], ['year', '2000']];


function fromListToObject(array) {  
  var cars = [];
    for(var j = 0; j < array.length/3; j++){ 
      var obj = {};
      for (var i = j; i <= j+3; i++) { 
        var arr1 = array[i];
        obj[arr1[0]] = arr1[1];
      }
      cars.push(obj)
    }
  return cars;
}

var output = fromListToObject(array);
console.log(output);

answered Jul 13, 2017 at 10:43

Hassan Imam

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Comments

uingtea · Accepted Answer · 2017-07-13 11:36:29Z

0

return full object

{ 
'0': { make: 'Ford', model: 'Mustang', year: '1964' },
'1': { make: 'Honda', model: 'CRV', year: '2000' }
}

var array = [
  ['make', 'Ford'],
  ['model', 'Mustang'],
  ['year', '1964'],
  ['make', 'Honda'],
  ['model', 'CRV'],
  ['year', '2000']
];

function fromListToObject(array) {
  var obj = {};
  var child_obj = {};
  var objindex = 0;
  var index = 0;
  while(array.length) {
    while(array.length && index < 3){
      var arr1 = array.shift();
      child_obj[arr1[0]] = arr1[1];
      index++;
    }
    index = 0;
    obj[objindex]= child_obj;
    child_obj = {};
    objindex++;
  }
  return obj;
}

var result = fromListToObject(array);
console.log(result);

answered Jul 13, 2017 at 11:36

uingtea

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