Flatten JSON objects in JavaScript

Question

I have a JSON response and I need to flatten some objects according to conditions.

In my case, the condition is if object === "$"

I also need to flatten some array to string only. What is the best way to manage this? Any lib recommendations?

The final goal would be to use it as a GraphQL schema.

The JSON response is:

[
   {
      "$":{
         "product_id":"110015888426488829026466000222",
         "name":"Belstaff Trialmaster Pro W Motorradjacke Schwarz",
         "sku_number":"B000134394",
         "manufacturer_name":"BELSTAFF",
         "part_number":"42050011L81N03379005436"
      },
      "discount":[
         {
            "$":{
               "currency":"EUR"
            },
            "type":[
               "amount"
            ]
         }
      ],
      "price":[
         {
            "$":{
               "currency":"EUR"
            },
            "sale":[
               "1195.00"
            ],
            "retail":[
               "1195.00"
            ]
         }
      ],
      "shipping":[
         {
            "cost":[
               {
                  "$":{
                     "currency":"EUR"
                  },
                  "amount":[
                     "0.00"
                  ],
                  "currency":[
                     "EUR"
                  ]
               }
            ],
            "information":[
               "3–7 Werktage"
            ],
            "availability":[
               "in-stock"
            ]
         }
      ],
      "attributeClass":[
         {
            "$":{
               "class_id":"60"
            },
            "Product_Type":[
               "Motorcycle"
            ],
            "Size":[
               "36,38,40,42,44,46,48"
            ],
            "Material":[
               "Waxed Leather"
            ],
            "Color":[
               "Schwarz"
            ],
            "Gender":[
               "Female"
            ],
            "Age":[
               "Adult"
            ]
         }
      ]
   },
   ...
]

And I want

[
   {
      "product_id":"110015888426488829026466000222",
      "name":"Belstaff Trialmaster Pro W Motorradjacke Schwarz",
      "sku_number":"B000134394",
      "manufacturer_name":"BELSTAFF",
      "part_number":"42050011L81N03379005436"
      "discount":{
          "currency":"EUR"
          "type":"amount"
      },
      "price":{
         "currency": "EUR",
         "sale": "1195.00",
         "retail": "1195.00"
      },
      "shipping":[
         "cost":{
            "currency": "EUR"
            "amount": "0.00",
            "currency": "EUR"
         },
         "information":"3–7 Werktage",
         "availability": "in-stock"
      ],
      "attributeClass":{
         "class_id":"60",
         "Product_Type": "Motorcycle",
         "Size": "36,38,40,42,44,46,48",
         "Material": "Waxed Leather",
         "Color": "Schwarz",
         "Gender": "Female",
         "Age": "Adult"
      }
   },
   ...
]

What I tried:

const flatJson = async data => {
  try {
    const newData = await Promise.all(json.map( async (item, i) => {
      xxx
    }));
    return newData
  }
  catch(err) {
    console.log(err)
  }
};

do you have always only one object in the arrays? what should happen, if not? btw, what have you tried? — Nina Scholz
– Nina Scholz, Commented Apr 18, 2020 at 9:01
Cant you change your json response from backend to not include arrays for only single object? and make it clean? — M A Salman
– M A Salman, Commented Apr 18, 2020 at 9:10
@NinaScholz Yes, there is multiple object in the array. I edit my post with what I tried. — arnaudjnn
– arnaudjnn, Commented Apr 18, 2020 at 11:09

Nina Scholz · Accepted Answer · 2020-04-18 09:39:43Z

You could convert the various types to single objects.

const convert = object => {
    if (!object || typeof object !== 'object') return object;
    if (Array.isArray(object)) {
        return object.every(v => typeof v === 'string')
            ? object.join()
            : Object.assign({}, ...object.map(convert));
    }
    return Object.fromEntries(Object.entries(object).flatMap(([k, v]) =>
        k === '$'
            ? Object.entries(v).map(([k, v]) => [k, convert(v)])
            : [[k, convert(v)]]
    ));
};

var data = [{ $: { product_id: "110015888426488829026466000222", name: "Belstaff Trialmaster Pro W Motorradjacke Schwarz", sku_number: "B000134394", manufacturer_name: "BELSTAFF", part_number: "42050011L81N03379005436" }, discount: [{ $: { currency: "EUR" }, type: ["amount"] }], price: [{ $: { currency: "EUR" }, sale: ["1195.00"], retail: ["1195.00"] }], shipping: [{ cost: [{ $: { currency: "EUR" }, amount: ["0.00"], currency: ["EUR"] }], information: ["3–7 Werktage"], availability: ["in-stock"] }], attributeClass: [{ $: { class_id: "60" }, Product_Type: ["Motorcycle"], Size: ["36,38,40,42,44,46,48"], Material: ["Waxed Leather"], Color: ["Schwarz"], Gender: ["Female"], Age: ["Adult"] }] }],
    result = data.map(convert);

console.log(result);

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

Dickens A S · Accepted Answer · 2020-04-18 09:44:10Z

You can try this recursion code

function recurseData(data, level) {
    var newdata = {};
    for(var prop in data) {
        if( data[prop].constructor == Object && prop=="$") {
            var data1 = recurseData(data[prop], level+1);
            for(var prop1 in data1)
                newdata[prop1] = data1[prop1];
        }
        else if(data[prop].constructor == Object){
            newdata[prop] = recurseData(data[prop],level+1);
        }
        else if(data[prop].constructor == Array && level > 0 && data[prop][0].constructor != Object && data[prop].length==1){
            newdata[prop] = data[prop][0];
        }
        else if(data[prop].constructor == Array) {
            newdata[prop] = [];
            for(var i=0;i<data[prop].length;i++)
                newdata[prop].push( recurseData(data[prop][i],level+1) );
        }
        else if(prop!="$")
            newdata[prop] = data[prop];
    }
    return newdata;
}

data[0] = recurseData(data[0], 0);

is simple loops through all tree structure and detects for a key $

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