javascript - Remove null attributes from an Object in Typescript - Stack Overflow

admin管理员组

文章数量:1356702

As reference Remove blank attributes from an Object in Javascript, how to make it Typescript patible?

JS function (nested objects | ES10):

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

I've tried with Exclude<T, null> but it doesn't works with nested objects and I think it's not the correct utility to use.

Note that the returned type should remove null type(s) but keeps undefined.

Example/Expected behaviour:

type TestType = {
  a?: {
    b?: {
      c: string;
    } | null;
    z?: {
      x: string;
    };
  } | null;
};

const testObj: TestType = {
  a: {
    b: null,
    z: { x: 'Hi' }
  }
};

const resultObj = removeEmpty(testObj);

Where resultObj type is similar to:

type ResultTestTypeExample = {
  a?: {
    b?: {
      c: string;
    };
    z?: {
      x: string;
    };
  };
};

As reference Remove blank attributes from an Object in Javascript, how to make it Typescript patible?

JS function (nested objects | ES10):

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

I've tried with Exclude<T, null> but it doesn't works with nested objects and I think it's not the correct utility to use.

Note that the returned type should remove null type(s) but keeps undefined.

Example/Expected behaviour:

type TestType = {
  a?: {
    b?: {
      c: string;
    } | null;
    z?: {
      x: string;
    };
  } | null;
};

const testObj: TestType = {
  a: {
    b: null,
    z: { x: 'Hi' }
  }
};

const resultObj = removeEmpty(testObj);

Where resultObj type is similar to:

type ResultTestTypeExample = {
  a?: {
    b?: {
      c: string;
    };
    z?: {
      x: string;
    };
  };
};

• javascript
• typescript
• null
• undefined

Share Improve this question Follow edited May 11, 2022 at 16:03 Carlo Corradini asked May 11, 2022 at 15:55 Carlo CorradiniCarlo Corradini 3,45533 gold badges2222 silver badges2828 bronze badges

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 6

Does this work for you?

type ExpandRecursively<T> = T extends object
  ? T extends infer O ? { [K in keyof O]: ExpandRecursively<O[K]> } : never
  : T;

type RemoveNull<T> = ExpandRecursively<{ [K in keyof T]: Exclude<RemoveNull<T[K]>, null> }>

Usage:

function removeEmpty<T extends object>(obj: T): RemoveNull<T> {
  return Object.fromEntries(
    Object.entries(obj)
      .filter(([_, v]) => v != null)
      .map(([k, v]) => [k, v === Object(v) ? removeEmpty(v) : v])
  ) as RemoveNull<T>
}

Playground

export function removeNull<T extends object>(obj: T | any) {
  Object.keys(obj).forEach(k => {
    const key = k as keyof T
    if (obj[key] && typeof obj[key] === 'object') removeNull(obj[key])
    else if (obj[key] == null) delete obj[key]
  })
  return obj
}

You can remove null elements with the code above. You can also give your type and it will remove all nested objects properties

本文标签： javascriptRemove null attributes from an Object in TypescriptStack Overflow