Method for recreating array of objects returns same array of same object repeated

Question

I am working on a function that will take an array of flattened nested objects and return another array, with the object attributes renamed.

For example, this input:

[

{
 id: 13,
 student_name: 'John',
 parents.mother: 'Mia',
 parents.father: 'Milo',
 parents.mother.mother_education: 'msc',
 parents.father.father_education: 'bachelor',
},
{
 id: 13,
 student_name: 'Erica',
 parents.mother: 'Lea',
 parents.father: 'Theo',
 parents.mother.mother_education: 'bachelor',
 parents.father.father_education: 'high school',
},
......

]

should return:

[

{
 id: 13,
 student_name: 'John',
 mother: 'Mia',
 father: 'Milo',
 mother_education: 'msc',
 father_education: 'bachelor',
},
{
 id: 13,
 student_name: 'Erica',
 mother: 'Lea',
 father: 'Theo',
 mother_education: 'bachelor',
 father_education: 'high school',
},
......

]

The code so far:

function format_object(myobj){

    var raw_result = []; //the final variable - an array of objects
    var raw_obj = {}; //every object is kept here temporarly
    var depth = 0; //depth of the attribute name

    for(var i = 0; i< myobj.length; i++){ //for each object
        for(var attributename in myobj[i]){ //for each attribute
            depth = attributename.split(".").length-1; //calculate name depth
            if(depth == 0){ 
                raw_obj[attributename] = myobj[i][attributename]; //for simple attribute names, just copy them on the temp object
            }
            else{
                new_attribute = attributename.split('.')[depth] //for complex names, split last word
                raw_obj[new_attribute] = myobj[i][attributename];
            }
        }
        raw_result.push(raw_obj); //add the object we just created into the final variable
    }
    return raw_result;
}

Printing the raw_object I create, I get the correct object in each iteration. However , the final variable is composed of only the first object, repeated n times.

charlietfl · Accepted Answer · 2017-02-07 19:34:57Z

3

you need a new raw_object in each iteration of the loop, otherwise you are constantly changing properties of the same object.

When you push an object to the array it pushes a reference , not a copy .

So you are ending up with an array where each element is a reference to the exact same single object

var raw_result = []; //the final variable - an array of objects   
var depth = 0; //depth of the attribute name

for(var i = 0; i< myobj.length; i++){ //for each object

    var raw_obj = {}; // new object
    .....

edited Feb 7, 2017 at 19:34

answered Feb 7, 2017 at 19:28

charlietfl

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Comments

Nina Scholz · Accepted Answer · 2017-02-07 19:38:59Z

2

You could iterate the array and take the keys of the object, split them and take the last item for a new object and the value.

var data = [{ id: 13, 'student_name': 'John', 'parents.mother': 'Mia', 'parents.father': 'Milo', 'parents.mother.mother_education': 'msc', 'parents.father.father_education': 'bachelor', }, { id: 13, 'student_name': 'Erica', 'parents.mother': 'Lea', 'parents.father': 'Theo', 'parents.mother.mother_education': 'bachelor', 'parents.father.father_education': 'high school' }],
    newArray = data.map(function (o) {
        return Object.keys(o).reduce(function (r, k) {
            r[k.split('.').pop()] = o[k];
            return r;
        }, {});
    });
    
console.log(newArray);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Feb 7, 2017 at 19:38

answered Feb 7, 2017 at 19:32

Nina Scholz

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Comments

Pranav C Balan · Accepted Answer · 2017-02-07 19:49:02Z

I think this can be much simpler using Array#map and Array#reduce methods.

// iterate over the object array
var res = data.map(function(obj) {
  // get all keys from object and iterate over the object 
  // to generate the updated object
  return Object.keys(obj).reduce(function(o, k) {
    // define the object property by splitting property name
    // and getting the last part
    o[k.split('.').pop()] = obj[k];
    // return the object reference
    return o;
    // define initial value as an empty object
  }, {});
})

var data = [

  {
    id: 13,
    student_name: 'John',
    'parents.mother': 'Mia',
    'parents.father': 'Milo',
    'parents.mother.mother_education': 'msc',
    'parents.father.father_education': 'bachelor',
  }, {
    id: 13,
    student_name: 'Erica',
    'parents.mother': 'Lea',
    'parents.father': 'Theo',
    'parents.mother.mother_education': 'bachelor',
    'parents.father.father_education': 'high school',
  }
]


var res = data.map(function(obj) {
  return Object.keys(obj).reduce(function(o, k) {
    o[k.split('.').pop()] = obj[k];
    return o;
  }, {});
})


console.log(res);

The actual problem lies in your code is that you are using the same object again and again in each iteration so all the elements refer to a single object. To resolve that you need to reinitialize within the loop for a new element.

for(var i = 0; i< myobj.length; i++){
   var raw_obj = {};
   // rest of your code

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