Recursively replace keys within an object of unknown size using Javascript

Question

I would like to be able to replace certain keys within an object of dynamic size using Javascript. For example, I have an object that might look like this:

var obj = {
    where: {
        hypes: {
            lte: 12 <-- replace key
        },
        or: [
            {
                hypes: {
                    lt: 14 <-- replace key
                }
            },
            {
                id: {
                    lt: 10 <-- replace key
                }
            }
        ]
    } 
}

In order for this object to be used with Sequelize I need to convert the following keys to Sequelize operators: lt, or, and lte. I've created an operators object that acts as a dictionary so I can pull the Sequelize operator from it:

const operators = {
    'eq': [Op.eq],
    'lte': [Op.lte],
    'lt': [Op.lt],
    'or': [Op.or]
};

I was thinking I could use the operators object to match the key of the obj and replace it with the value of the operators object. I figured I could use the following recursive function to loop through the obj given its unknown size:

const iterate = (obj) => {
    Object.keys(obj).forEach(key => {

    console.log(`key: ${key}, value: ${obj[key]}`)

    if (typeof obj[key] === 'object') {
            iterate(obj[key])
        }
    })
}

The above function will check if the value of a key is an object and will call the iterate() method again.

Thus I can call: iterate(obj) and it'll recursively map through all nested properties in the object.

The issue I am having is how do I replace the keys when they match a property inside the operators object so that I'll end up with an obj that looks like this:

var obj = {
    where: {
        hypes: {
            lte: 12
        },
        [Op.or]: [ <-- changed
            {
                hypes: {
                    [Op.lt]: 14 <-- changed
                }
            },
            {
                id: {
                    [Op.lt]: 10 <-- changed
                }
            }
        ]
    } 
}

Thanks!

Nina Scholz · Accepted Answer · 2019-12-28 09:12:11Z

1

You could take a recursive approach.

function replace(object) {
    return Array.isArray(object)
        ? object.map(replace)
        : object && typeof object === 'object'
            ? Object.fromEntries(Object
                .entries(object)
                .map(([k, v]) => [k in operators ? operators[k] : k, replace(v)])
            )
            : object;
}

var obj = { where: { hypes: { lte: 12 }, or: [{ hypes: { lt: 'xx' } }, { id: { lt: 10 } }] } };

const operators = { eq: '[Op.eq]', lte: '[Op.lte]', lt: '[Op.lt]', or: '[Op.or]' };

console.log(replace(obj));

edited Dec 28, 2019 at 9:12

answered Dec 27, 2019 at 19:38

Nina Scholz

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1 Comment

Jordan Lewallen Over a year ago

Love this recursive approach! Thank you so much, small typo in the answer though. There should be a semicolon after the obj instead of a comma. Anyways this had me stumped, I appreciate the help!

Riddhesh Markandeya · Accepted Answer · 2019-12-27 19:46:45Z

0

In your recursive function when you hit the leaf, you can change the key and delete the older one.

var obj = {
  where: {
    hypes: {
      lte: 12
    },
    or: [{
        hypes: {
          lt: 14
        }
      },
      {
        id: {
          lt: 10
        }
      }
    ]
  }
};

const operators = {
  eq: '[Op.eq]',
  lte: '[Op.lte]',
  lt: '[Op.lt]',
  or: '[Op.or]'
};

const iterate = (obj) => {
  Object.keys(obj).forEach(key => {
    // console.log(`key: ${key}, value: ${obj[key]}`)
    if (typeof obj[key] === 'object') {
      iterate(obj[key])
    }
    if (operators[key]) {
      obj[operators[key]] = obj[key];
      delete obj[key];
    }
  });
};

iterate(obj)
console.log(obj)

answered Dec 27, 2019 at 19:46

Riddhesh Markandeya

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