Can't transform from one value in a nested Array into another JavaScript

Question

The task is the following:

Write a function called "transformEmployeeData" that transforms some employee data from one format to another.

The argument will look something like this:

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

Given that input, the return value should look like this:

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

Note that the input may have a different number of rows or different keys than the given sample.

For example, let's say the HR department adds a "tshirtSize" field to each employee record. Your code should flexibly accommodate that.

I tried this:

function transformEmployeeData(array) {

  var obj = {}, arr = [];

    array.forEach(function(cv){
          for(var i = 0, l = cv.length; i < l; i++) {
                obj[cv[i][0]] = cv[i][1];

          }
       arr.push(obj);
    });

  return arr
}

I got back two objects but they're both {firstName: 'Mary', lastName: 'Jenkins', age: 36, role: 'manager'}

I thought doing this in the body of the loop would solve the problem because I thought (wrongly) it was a scope issue.

(function(i){
   obj[cv[i][0]] = cv[i][1];
}(i));

Any help will be appreciated as always!

Your inner for loop could have been cv.forEach. There's no need to write explicit loops like that anymore for arrays. — castletheperson
– castletheperson, Commented Apr 20, 2017 at 23:52
@4castle Is it because of speed? It did dawn on me but sometimes I can't help why my brain pan defers to different patterns... — Antonio Pavicevac-Ortiz
– Antonio Pavicevac-Ortiz, Commented Apr 20, 2017 at 23:55
It's not so much about speed, but about having more declarative code. Say what and not how. — castletheperson
– castletheperson, Commented Apr 21, 2017 at 0:01

chris · Accepted Answer · 2017-04-20 23:44:56Z

2

You are correct it is a scope issue. You should define a new obj in each iteration of the forEach, not outside it.

function transformEmployeeData(array) {
    var arr = [];
    array.forEach(function(cv){
        var obj = {};
        for(var i = 0, l = cv.length; i < l; i++) {
            obj[cv[i][0]] = cv[i][1]; 
        }
        arr.push(obj);
    });

  return arr
}

edited Apr 20, 2017 at 23:44

answered Apr 20, 2017 at 23:39

chris

6,8436 gold badges43 silver badges54 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

ibrahim mahrir · Accepted Answer · 2017-04-20 23:44:59Z

function transform(arr) {                    
  return arr.map(function(sub) {             // for each subarray sub of the array arr
    return sub.reduce(function (obj, a) {    // create a new object obj
      obj[a[0]] = a[1];                      // set the key in a[0] to the value a[1]
      return obj;
    }, {});
  });
}

var array = [[["firstName","Joe"],["lastName","Blow"],["age",42],["role","clerk"]],[["firstName","Mary"],["lastName","Jenkins"],["age",36],["role","manager"]]];

console.log(transform(array));

Or even shorter in recent ECMAScript versions:

function transform(arr) {                    
  return arr.map(sub => sub.reduce((obj, a) => (obj[a[0]] = a[1], obj), {}));
}

var array = [[["firstName","Joe"],["lastName","Blow"],["age",42],["role","clerk"]],[["firstName","Mary"],["lastName","Jenkins"],["age",36],["role","manager"]]];

console.log(transform(array));

Collectives™ on Stack Overflow

Can't transform from one value in a nested Array into another JavaScript

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related