Flattening the first element of array with nested objects in JavaScript-CodePudding

I parsed an XML data into a JS obj, causing all parent tags to turn into an array. I tried flattening it but I can't seem to wrap my head around the recursion part however.

Here's a sample of the nested object:

nestedObj: [
   {
   foo1:[ "A" ],
   foo2: [
    {
     bar1: [ "B" ],
     bar2: [ "C" ]    
    }
   ], 
   foo3: [ "D" ]
   .
   .
   .
   }
]

expectedData: {
   foo1: "A" ,
   foo2:
    {
     bar1: "B",
     bar2: "C"    
    }
   , 
   foo3: "D"
 .
 .
 .
}

Here's my attempt at the code:

function flattenArrToObj(arr) {
  for(let key in arr) {
    let val = arr[key];
    if(Array.isArray(val)) {
      arr[key] = val[0];
    } else {
     flattenArrToObj(val);
    }
  }
  return arr[0];
}

It works fine on the inner data such as bar1 and bar2 but as you can see, I still have to return arr[0] to accomplish what I wanted in the first place - which is somewhat contradicting to the effort of recursion. Any thoughts on this?

CodePudding user response：

You could have a look to array and objects.

const
    getObject = object => Object.fromEntries(Object
        .entries(object)
        .map(([k, v]) => [k, fn(v)])
    ),
    fn = value => {
        if (Array.isArray(value)) {
            return typeof value[0] === 'object'
                ? Object.assign({}, ...value.map(getObject))
                : value.length === 1
                    ? value[0]
                    : value
        }
        return getObject(value);
    }
    source = [{ foo1: ["A"], foo2: [{ bar1: ["B"], bar2: ["C"] }], foo3: ["D"] }],
    result = fn(source); 

console.log(result);

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

CodePudding user response：

Per the sample data, each array has one value. Hence the use of [0]. The following code use a combination of recursion, Object.fromEntries() and Object.entries() to traverse the object.

const nestedObj = [
   {
   foo1:[ "A" ],
   foo2: [
    {
     bar1: [ "B" ],
     bar2: [ "C" ]    
    }
   ], 
   foo3: [ "D" ]
   }
];

const arrToObj = val => {
    let vals = Array.isArray(val) ? arrToObj(val[0]) : val;
    if (typeof vals === 'object') {
        return Object.fromEntries( Object.entries( vals ).map(([k, v]) => [k, arrToObj(v)]) );
    } else {
        return vals;
    }
};

const newObj = arrToObj(nestedObj);

console.log( newObj );

/* OUTPUT
{
  "foo1": "A",
  "foo2": {
    "bar1": "B",
    "bar2": "C"
  },
  "foo3": "D"
}
*/