Array to object in Javascript

Question

I'm working on a little problem in JS (not graded or for school, just for practice), and can't seem to get it quite right.

The aim is to write a function that converts a multi-dimensional array to an array of objects. For example, the input could be:

var data = [
  [
    ['firstName', 'Joe'], ['lastName', 'Blow'], ['age', 42], ['role', 'clerk']
],
[
    ['firstName', 'Mary'], ['lastName', 'Jenkins'], ['age', 36], ['role', 'manager']
  ]
]

And this should be the output:

[
{firstName: 'Joe', lastName: 'Blow', age: 42, role: 'clerk'},
{firstName: 'Mary', lastName: 'Jenkins', age: 36, role: 'manager'}
]

Here is what I have so far:

function transformEmployeeData(array) {
  var object = {};
  var objectsArray = [];
  for (i=0; i<array.length; i++) {
    for (j=0; j<array[i].length; j++) {
      var keys = array[i][j][0];
      object[keys] = array[i][j][1];
     }    objectsArray.push(object);
   } 
       return objectsArray);
 }

It's almost right, but I get this as output:

[ { firstName: 'Mary',
lastName: 'Jenkins',
age: 36,
role: 'manager' },
{ firstName: 'Mary',
lastName: 'Jenkins',
age: 36,
role: 'manager' } ]

How do I go about fixing the function so that it doesn't spit out the same thing twice?

Thanks for your help!

Have you tried going through the code with a debugger, or with pen and paper? That way you can understand where the bug lies and fix it. — Andrew Li
– Andrew Li, Commented May 8, 2017 at 22:54

khan · Accepted Answer · 2017-05-08 22:59:01Z

2

Your code creates a single instance of an object, then overwrites the values in that instance.

To fix, create a new object every time:

function transformEmployeeData(array) {
    var objectsArray = [];
    for (i=0; i<array.length; i++) {
       var object = {};
       for (j=0; j<array[i].length; j++) {
           var keys = array[i][j][0];
           object[keys] = array[i][j][1];
       }    
       objectsArray.push(object);
  } 
  return objectsArray);
}

edited May 8, 2017 at 22:59

answered May 8, 2017 at 22:57

khan

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1 Comment

user211309 Over a year ago

Thanks so much! I thought that was the problem, but didn't know what to do about it. Nice fix!

Imbar M. · Accepted Answer · 2017-05-08 22:55:07Z

1

you're only creating 1 instance of the object variable. create a new instance ( object = {} ) inside the loop.

you are ovirriding the properties of the object each run, but actually using the same object.

answered May 8, 2017 at 22:55

Imbar M.

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