Javascript - transpose dict into array

Question

I have a the following dict I would like to transpose:

dict = {
         'column1': [1, 2, 3],
         'column2': [4, 5, 6],
         'column3': [7, 8, 9]
        }

Into:

transposed_array = [
                    [1, 4, 7],
                    [2, 5, 8],
                    [3, 6, 9]
                  ]

Objects don't have a strict order, do you expect them to sort alphabetically? — Etheryte, May 26 '15 at 13:09
And what part of this have you had trouble doing? This is a requirement, but you're missing an actual question. — Sam Hanley, May 26 '15 at 13:09
@Nit Not alphabetically, I guess (think about column9 and column10) — Denys Séguret, May 26 '15 at 13:10

score 1 · Accepted Answer · edited May 23 '17 at 11:51

1

Here's a solution (updated for non square matrices):

var dict = {
     'column1': [1, 2, 3],
     'column2': [4, 5, 6],
     'column3': [7, 8, 9]
}
var keys = Object.keys(dict);
var transposedMatrix = dict[keys[0]].map(function(col,i){  
  return keys.map(function(_,j){ return dict[keys[j]][i] })
});

Demonstration

Note that this code assumes that objects do have ordered keys, which has always been the case in all known ES implementations and is now normalized by ES6.

edited May 23 '17 at 11:51

Community

1
1

answered May 26 '15 at 13:16

Denys Séguret

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This answer seems fine. Interested in the reason for downvoting – CodingIntrigue May 26 '15 at 13:22
1

@RokoC.Buljan [Why don't you just test](http://jsbin.com/ridonurivu/2/watch?js,console,output) ? ;) – Denys Séguret May 26 '15 at 13:23
@RGraham Object properties order **is** now guaranteed, and the spec follows what the browsers were already doing. – Denys Séguret May 26 '15 at 13:25
your solution does'nt work if the dict is different: ex `var dict = { 'column1': [1],'column2': [4], 'column3': [7]}` – Below the Radar May 26 '15 at 15:04
@BelowtheRadar I've edited with a version working with non square matrixes. – Denys Séguret May 26 '15 at 15:11

ozil · Answer 2 · 2015-05-26T14:31:17.340

var dict = {
         'column1': [1, 2, 3],
         'column2': [4, 5, 6],
         'column3': [7, 8, 9]
        };
var transposed_array =[];
for (key in dict){
    transposed_array.push(dict[key]);

}
console.log(transposed_array);

Demo
Updated:

var dict = {
         'column1': [1, 2, 3],
         'column2': [4, 5, 6],
         'column3': [7, 8, 9]
        };
var transposed_array =[];
for (key in dict){
    transposed_array.push(dict[key]);

}
function transposeArray(array){

    var newArray = [];
    for(var i = 0; i < array.length; i++){
        newArray.push([]);
    }

    for(var i = 0; i < array.length; i++){
        for(var j = 0; j < array[i].length; j++){
            newArray[j].push(array[i][j]);
        }
    }

    return newArray;
}
console.log(transposeArray(transposed_array));

Demo

data is not transposed – Below the Radar May 26 '15 at 14:00 — Below the Radar, May 26 '15 at 14:00
what does it mean `data is not transposed`?? – ozil May 26 '15 at 14:01 — ozil, May 26 '15 at 14:01

score 1 · Answer 3 · answered May 26 '15 at 15:19

basically first find the shared part of the keys, then the endings, after sort reassamle the array. the result is numerical orderd if number otherwise the order is maintained.

var dict = {
        'column3': [7, 8, 9],
        'column2': [4, 5, 6],
        'column1': [1, 2, 3]
    },
    keys = Object.keys(dict),
    samePart = keys.reduce(function (a, b) {
        var i = 0, l = Math.min(a.length, b.length);
        while (i < l && a[i] === b[i]) { i++; }
        return a.substr(0, i);
    }),
    otherPart = keys.map(function (e) { return e.slice(samePart.length); }).sort(function (a, b) { return a - b; }),
    transposedMatrix = [].map.call(otherPart, function (col, i) { return dict[samePart + col].map(function (_, j) { return dict[samePart + col][j]; }); });

Javascript - transpose dict into array

3 Answers3