Object/Since 1.38.0

filterObject

Creates a new object containing the properties that satisfy a predicate.

filterObject(object, predicate):Partial<T>

Parameters

objectTrequired

The object whose properties should be filtered.

predicate(value: T[keyof T], key: keyof T, object: T) => booleanrequired

A function called for each own enumerable string-keyed property. It receives the property value, key, and original object. Returning true includes the property in the result.

Returns

Partial<T>

Returns a new object containing only the properties for which the predicate returned true.

Examples

Basic usage

Keeps only properties whose values are numbers.

TypeScript

const result = filterObject(
  {
    name: "Alice",
    age: 25,
    score: 90,
  },
  (value) => typeof value === "number",
);

console.log(result);
// {
//   age: 25,
//   score: 90
// }

Filter by key

The predicate can inspect the property key.

TypeScript

const result = filterObject(
  {
    name: "Alice",
    age: 25,
    active: true,
  },
  (_value, key) => key !== "active",
);

console.log(result);
// {
//   name: "Alice",
//   age: 25
// }

Filter by value

The predicate receives each property's value.

TypeScript

const result = filterObject(
  {
    a: 5,
    b: 12,
    c: 20,
  },
  (value) => typeof value === "number" && value > 10,
);

console.log(result);
// {
//   b: 12,
//   c: 20
// }

Using the original object

The third predicate argument is the original object.

TypeScript

const result = filterObject(
  {
    min: 10,
    max: 20,
    value: 15,
  },
  (value, key, object) => {
    if (key === "value") {
      return (
        typeof value === "number" &&
        value >= object.min &&
        value <= object.max
      );
    }

    return false;
  },
);

console.log(result);
// {
//   value: 15
// }

No matches

If the predicate returns false for every property, an empty object is returned.

TypeScript

const result = filterObject(
  {
    a: 1,
    b: 2,
  },
  () => false,
);

console.log(result);
// {}

All matches

Returning true for every property copies all enumerable own string-keyed properties.

TypeScript

const result = filterObject(
  {
    name: "Alice",
    age: 25,
  },
  () => true,
);

console.log(result);
// {
//   name: "Alice",
//   age: 25
// }

Original object is unchanged

The function creates a separate result object and does not modify the input object.

TypeScript

const original = {
  name: "Alice",
  age: 25,
};

const result = filterObject(
  original,
  (value) => typeof value === "string",
);

console.log(original);
// {
//   name: "Alice",
//   age: 25
// }

console.log(result);
// {
//   name: "Alice"
// }

console.log(result === original);
// false

Inherited properties

Inherited properties are not processed because the implementation uses Object.keys.

TypeScript

const parent = {
  inherited: true,
};

const object = Object.create(parent);

object.own = true;

const result = filterObject(
  object,
  () => true,
);

console.log(result);
// {
//   own: true
// }

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