Return necessary value with recursion - Javascript

Question

I have following data:

    const section={
     fileds: [
     {
      child: [
        {
          fileds: [
            {
              id: "kxf5",
              label: null
            }
          ]
        },
        {
          fileds: [
            {
              id: "ed5t",
              label: "section"
            }
          ]
        },
        
      ]
    },
    {
      child: [
        {
          fileds: [
            {
              id: "ccfr",
              label: null
            }
          ]
        },
        {
          fileds: [
            {
              id: "kdpt8",
              label: "section"
            }
          ]
        },
        
      ]
    },
    
     ]
    }

I need to return all id in array and I should use recursion.

I have try following code.

const section={fileds: [{child: [{fileds: [{id: "kxf5",label: null}]},{fileds: [{id: "ed5t",label: "section"}]},]},{child: [{fileds: [{id: "ccfr",label: null}]},{fileds: [{id: "kdpt8",label: "section"}]},]},]}
function printId(value, child ) {
  return [value, ...(child ? printList(child) : [])]
}

console.log(printId(section.fields));

But it not helped me.

Is there a way to solve this problem with recursion? Please help to fix this.

The final result should be like ["kxf5","ed5t","ccfr", "kdpt8"] this.

You have a typo in your code: fileds.

user16540390
– user16540390

2022-04-26 13:38:44 +00:00
Commented Apr 26, 2022 at 13:38 — user16540390
– user16540390, Commented Apr 26, 2022 at 13:38

0stone0 · Accepted Answer · 2022-04-26 14:06:00Z

1

An other way, using reduce() to recursively fill an array

const section= {fileds: [{child: [{fileds: [{id: "kxf5", label: null } ] }, {fileds: [{id: "ed5t", label: "section"} ] }, ] }, {child: [{fileds: [{id: "ccfr", label: null } ] }, {fileds: [{id: "kdpt8", label: "section"} ] }, ] }, ] }

function printId(value) {
    return value.reduce((prev, cur) => {
        if (cur.id) {
            return [ ...prev, cur.id ];
        } else {
            let key = ('child' in cur) ? 'child' : 'fileds';
            return [ ...prev, ...printId(cur[key]) ]
        }
    }, []);
}

console.log(printId(section.fileds));

answered Apr 26, 2022 at 14:06

0stone0

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Comments

jsN00b · Accepted Answer · 2022-04-26 14:43:54Z

A better solution could be this one:

// recursive method to extract "id"s
function getId(o) {
  // if current parameter "o" has "id" prop, return it
  if (o.id) return o.id;
  // else, iterate over "o" and recurse for each "value" of "o"
  return Object.keys(o).flatMap((key) => getId(o[key]));
}
const section = {
  fileds: [{
      child: [{
          fileds: [{
            id: "kxf5",
            label: null
          }]
        },
        {
          fileds: [{
            id: "ed5t",
            label: "section"
          }]
        },

      ]
    },
    {
      child: [{
          fileds: [{
            id: "ccfr",
            label: null
          }]
        },
        {
          fileds: [{
            id: "kdpt8",
            label: "section"
          }]
        },

      ]
    },

  ]
};

console.log(getId(section));

jsN00b · Accepted Answer · 2022-04-26 13:39:25Z

Below is one possible way to achieve the target.

Code Snippet

// recursively get only "id"s
const getIds = arr => (
  // implicit return of below result
  // iterate using ".flatMap()" to avoid nested result
  arr.flatMap(obj => {
    // extract values that are arrays
    const arrArrs = Object.values(obj).filter(v => Array.isArray(v));
    // extract values for key "id"
    const arrVals = Object.entries(obj).filter(
      ([k, v]) => typeof v === 'string' && k === "id"
    ).map(([k, v]) => v);
    // return "id" values, and then recursively call getIds for each "ar" (array)
    return [...arrVals, ...arrArrs.flatMap(ar => getIds(ar))]
  })
);

const section = {
  fileds: [{
      child: [{
          fileds: [{
            id: "kxf5",
            label: null
          }]
        },
        {
          fileds: [{
            id: "ed5t",
            label: "section"
          }]
        },

      ]
    },
    {
      child: [{
          fileds: [{
            id: "ccfr",
            label: null
          }]
        },
        {
          fileds: [{
            id: "kdpt8",
            label: "section"
          }]
        },

      ]
    },

  ]
};

console.log(getIds(section.fileds));

Explanation

Inline comments added in the snippet above.

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