Remove blank attributes from an Object in Javascript

Question

How do I remove all attributes which are undefined or null in a JavaScript object?

(Question is similar to this one for Arrays)

Answer 1

ES10/ES2019 examples

A simple one-liner (returning a new object).

let o = Object.fromEntries(Object.entries(obj).filter(([_, v]) => v != null));

Same as above but written as a function.

function removeEmpty(obj) {
  return Object.fromEntries(Object.entries(obj).filter(([_, v]) => v != null));
}

This function uses recursion to remove items from nested objects.

function removeEmpty(obj) {
  return Object.fromEntries(
    Object.entries(obj)
      .filter(([_, v]) => v != null)
      .map(([k, v]) => [k, v === Object(v) ? removeEmpty(v) : v])
  );
}

ES6/ES2015 examples

A simple one-liner. Warning: This mutates the given object instead of returning a new one.

Object.keys(obj).forEach((k) => obj[k] == null && delete obj[k]);

A single declaration (not mutating the given object).

let o = Object.keys(obj)
  .filter((k) => obj[k] != null)
  .reduce((a, k) => ({ ...a, [k]: obj[k] }), {});

Same as above but written as a function.

function removeEmpty(obj) {
  return Object.entries(obj)
    .filter(([_, v]) => v != null)
    .reduce((acc, [k, v]) => ({ ...acc, [k]: v }), {});
}

This function uses recursion to remove items from nested objects.

function removeEmpty(obj) {
  return Object.entries(obj)
    .filter(([_, v]) => v != null)
    .reduce(
      (acc, [k, v]) => ({ ...acc, [k]: v === Object(v) ? removeEmpty(v) : v }),
      {}
    );
}

Same as the function above, but written in an imperative (non-functional) style.

function removeEmpty(obj) {
  const newObj = {};
  Object.entries(obj).forEach(([k, v]) => {
    if (v === Object(v)) {
      newObj[k] = removeEmpty(v);
    } else if (v != null) {
      newObj[k] = obj[k];
    }
  });
  return newObj;
}

ES5/ES2009 examples

In the old days things were a lot more verbose.

This is a non recursive version written in a functional style.

function removeEmpty(obj) {
  return Object.keys(obj)
    .filter(function (k) {
      return obj[k] != null;
    })
    .reduce(function (acc, k) {
      acc[k] = obj[k];
      return acc;
    }, {});
}

This is a non recursive version written in an imperative style.

function removeEmpty(obj) {
  const newObj = {};
  Object.keys(obj).forEach(function (k) {
    if (obj[k] && typeof obj[k] === "object") {
      newObj[k] = removeEmpty(obj[k]);
    } else if (obj[k] != null) {
      newObj[k] = obj[k];
    }
  });
  return newObj;
}

And a recursive version written in a functional style.

function removeEmpty(obj) {
  return Object.keys(obj)
    .filter(function (k) {
      return obj[k] != null;
    })
    .reduce(function (acc, k) {
      acc[k] = typeof obj[k] === "object" ? removeEmpty(obj[k]) : obj[k];
      return acc;
    }, {});
}