Question 51094 in Javascript Question posted in
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Convert Array to Object – With special conditions – Javascript

I am trying to write a function that will convert an array that starts with ‘and’ | ‘or’ then process the next elements in the same level until the next ‘and’ | ‘or’. It will be more clear in the following example:

// from
[
  'and',
  1,
  2,
  'or',
  3,
  4,
],

// to
{ and: [
    1,
    2,
    {
        or: [
            3,
            4
        ]
    }
  ]
}

any thoughts?

Tags:

3

Answers


  1. 0

    This can be achieved with the recursive function just like below:

    function convertArrayToObject(arr) {
  let obj = {};
  let currentKey = null;

  for (let i = 0; i < arr.length; i++) {
    const item = arr[i];

    if (item === 'and' || item === 'or') {
      currentKey = item;
      if (!obj[currentKey]) {
        obj[currentKey] = [];
      }
    } else {
      if (currentKey) {
        if (typeof item === 'object' && item !== null) {
          obj[currentKey].push(convertArrayToObject(item));
        } else {
          obj[currentKey].push(item);
        }
      } else {
        if (typeof item === 'object' && item !== null) {
          obj = convertArrayToObject(item);
        }
      }
    }
  }

  return obj;
}

    This method should be called like below

    const arr = ['and', 1, 2, 'or', 3, 4];

const obj = convertArrayToObject(arr);

console.log(obj)  Output: { and: [ 1, 2, { or: [ 3, 4 ] } ] }
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  2. 0

    You can define a helper function and use reduce :

    const arrToObj = (arr) => {
const operator = arr[0];
const result = {[operator]: []};

arr.slice(1).reduce((current, val) => {
    if (val === 'and' || val === 'or') {
        return current[current.push({[val]: [] }) - 1][val];
    } else {
        current.push(val);
        return current;
    }
}, result[operator]);

return result;
};



const arr1 = ['and', 1, 2, 'or', 3, 4];
const obj1 = arrToObj(arr1);
console.log(obj1);

const arr2 = ['or', 1, 2, 'and', 3, 4];
const obj2 = arrToObj(arr2);
console.log(obj2);
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  3. 0

    Use Array.reduceRight() with a default value of an empty array. Reducing from the right means iterating from the last item to the first.

    If the item is a string, create a new object wrapped in array, with the item as a key, and the current accumulator (acc) as the value. If not prepend the item to the current accumulator array:

    const fn = arr => arr.reduceRight((acc, item) =>
  typeof item === 'string'
  ? [{ [item]: acc }] // create a new object inside a new array
  : [item, ...acc] // prepend the item to the current array
, [])

const [result] = fn(['and', 1, 2, 'or', 3, 4])

console.log(result)

    If you need a more granular approach (ie – some items may be strings), identify the "and" and "or" values:

    const isOperator = v => v === 'and' || v === 'or'

const fn = arr => arr.reduceRight((acc, v) =>
  isOperator(v)
  ? [{ [v]: acc }] // create a new object inside a new array
  : [v, ...acc] // prepend the item to the current array
, [])

const [result] = fn(['and', 1, 2, 'or', 3, 4])

console.log(result)
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