JS array of arrays to object

Question

I have a JS array (shown 4 examples actual has 66 )

[["A","Example1"],["A","Example2"],["B","Example3"],["B","Example4"]]

that I am trying to get into an object for a multi select drop down menu:

var opt = [{
label: 'A', children:[
        {"label":"Example1","value":"Example1","selected":"TRUE"},
        {"label":"Example2","value":"Example2","selected":"TRUE"} 
      ]
},

{
label: 'B', children:[
  {"label":"Example3","value":"Example3","selected":"TRUE"},
  {"label":"Example4","value":"Example4","selected":"TRUE"}
  ]
}
]

Is there a easy way to do this ?

It can be done with a single .reduce(), though "easy" is certainly relative, and as a result the answer to your question is a subjective "yes" or "no". Perhaps you could share your attempts or a specific difficulty you're encountering, so that we can help out as opposed to writing the code for for you :) — Tyler Roper
– Tyler Roper, Commented Dec 11, 2019 at 21:06
(For what it's worth I've removed all references to JSON in your question as well, including the title and tags, as it doesn't seem related.) — Tyler Roper
– Tyler Roper, Commented Dec 11, 2019 at 21:13
I'm currently trying to figure out a way to use For loops. starting with identifying the unique first value of the embedded arrays then loop through the arrays finding which match the list of unique values. — Tyger Guzman
– Tyger Guzman, Commented Dec 11, 2019 at 21:18
I think, instead of Array of objects, ES6 maps would make things easier. — sam
– sam, Commented Dec 11, 2019 at 21:20

Loc Mai · Accepted Answer · 2019-12-11 21:34:37Z

1

Updated: Using reduce() and filter() to get expected results.

const result = [['A', 'Example1'], ['A', 'Example2'], ['B', 'Example3'], ['B', 'Example4']].reduce((acc, cur) => {
  const objFromAccumulator = acc.filter((row) => row.label === cur[0]);
  const newChild = {label: cur[1], value: cur[1], selected: 'TRUE'};
  if (objFromAccumulator.length) {
    objFromAccumulator[0].children.push(newChild);
  } else {
    acc.push({label: cur[0], children: [newChild]});
  }
  return acc;
}, []);

console.log(result);

edited Dec 11, 2019 at 21:34

answered Dec 11, 2019 at 21:20

Loc Mai

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3 Comments

Tyger Guzman Over a year ago

this is great but backwards from what I'm trying to achieve. I'm wanting to go from the array of array to the 'label' format.

Loc Mai Over a year ago

@TygerGuzman Isn't the result an array of array to the label format from my answer? [["A", "Example1"], ["A", "Example2"], ["B", "Example3"], ["B", "Example4"]]

Tyger Guzman Over a year ago

I'm trying to go from [["A","Example1"],["A","Example2"],["B","Example3"],["B","Example4"]] to

[{ label: 'A', children:[         {"label":"Example1","value":"Example1","selected":"TRUE"},         {"label":"Example2","value":"Example2","selected":"TRUE"}        ] },  { label: 'B', children:[   {"label":"Example3","value":"Example3","selected":"TRUE"},   {"label":"Example4","value":"Example4","selected":"TRUE"}   ] } ]

Evan Trimboli · Accepted Answer · 2019-12-11 21:24:24Z

1

Something like this should work:

const raw = [["A","Example1"],["A","Example2"],["B","Example3"],["B","Example4"]];

const seen = new Map();
const processed = raw.reduce((arr, [key, label]) => {
    if (!seen.has(key)) {
        const item = {
            label: key,
            children: []
        };
        seen.set(key, item);
        arr.push(item);
    }
    seen.get(key).children.push({
        label,
        value: label,
        selected: "TRUE"
    })
    return arr;
}, []);
console.log(processed);

answered Dec 11, 2019 at 21:24

Evan Trimboli

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Comments

Klaycon · Accepted Answer · 2019-12-11 21:37:15Z

1

Here's a rather efficient and concise take on the problem using an object as a map:

const data = [["A","Example1"],["A","Example2"],["B","Example3"],["B","Example4"]];

const opt = data.reduce((results,[key,val]) => {
  if(!results[0][key]) //first element of results is lookup map of other elements
    results.push(results[0][key] = { label: key, children: [] });
  results[0][key].children.push({ label: val, value: val, selected:"TRUE" });
  return results;
}, [{}]).slice(1); //slice off map as it's no longer needed

console.log(opt);

edited Dec 11, 2019 at 21:37

answered Dec 11, 2019 at 21:24

Klaycon

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