filter
INFO
This function is only available in es-toolkit/compat
for compatibility reasons. It either has alternative native JavaScript APIs or isn’t fully optimized yet.
When imported from es-toolkit/compat
, it behaves exactly like lodash and provides the same functionalities, as detailed here.
Returns a new array of elements that satisfy the provided condition.
The condition can be specified in several ways:
- Predicate function: Runs a function for each element, selecting elements that satisfy the condition.
- Partial object: Selects elements that partially match the provided object.
- Property-value pair: Selects elements where a specified key matches a given value.
- Property name: Selects elements where the specified property name exists.
Signature
typescript
function filter<T>(arr: T[], doesMatch: (item: T, index: number, arr: T[]) => unknown): T[];
function filter<T>(arr: T[], doesMatch: Partial<T>): T[];
function filter<T>(arr: T[], doesMatch: [keyof T, unknown]): T[];
function filter<T>(arr: T[], doesMatch: string): T[];
function filter<T extends Record<string, unknown>>(
object: T,
doesMatch: (value: T[keyof T], key: keyof T, object: T) => unknown
): T[];
function filter<T extends Record<string, unknown>>(object: T, doesMatch: Partial<T[keyof T]>): T[];
function filter<T extends Record<string, unknown>>(object: T, doesMatch: [keyof T, unknown]): T[];
function filter<T extends Record<string, unknown>>(object: T, doesMatch: string): T[];
Parameters
arr
(T[]
) orobject
(T
): The array or object to iterate over.doesMatch
:For the first
filter
overload with arrays:- Predicate function (
(item: T, index: number, arr: T[]) => unknown
): A function to check if an element satisfies a condition. - Partial object (
Partial<T>
): A partial object that specifies the properties to match. - Property-value pair (
[keyof T, unknown]
): An array where the first element is the property key and the second element is the value to match. - Property name (
string
): The name of the property to check for in the elements.
- Predicate function (
For the
filter
overloads with objects:- Predicate function (
(value: T[keyof T], key: keyof T, object: T) => unknown
): A function that takes an value, its key, and the object, and returns a truthy value if the item matches the criteria. - Partial value (
Partial<T[keyof T]>
): A partial value to match against the values of the object. - Property-value pair (
[keyof T, unknown]
): An array where the first element is the property key and the second element is the value to match. - Property name (
string
): The name of the property to check for a truthy value.
- Predicate function (
Returns
(T[]
): An array of elements that satisfy the condition. If none, an empty array. ([]
)
Examples
Array
typescript
import { filter } from 'es-toolkit/compat';
// Using a predicate function
filter([1, 2, 3], n => n % 2 === 0);
// => [2]
// Using a partial object
const arr = [
{ id: 1, name: 'Alice' },
{ id: 2, name: 'Bob' },
];
filter(arr, { name: 'Bob' });
// => [{ id: 2, name: 'Bob' }]
// Using a property-value pair
const arr = [
{ id: 1, name: 'Alice' },
{ id: 2, name: 'Bob' },
];
filter(arr, ['name', 'Alice']);
// => [{ id: 1, name: 'Alice' }]
// Using a property name
const arr = [
{ id: 1, name: 'Alice' },
{ id: 2, name: 'Bob' },
{ id: 3, age: 28 },
];
filter(arr, 'name');
// => [{ id: 1, name: 'Alice' }, { id: 2, name: 'Bob' }]
Object
typescript
import { filter } from 'es-toolkit/compat';
// Using a predicate function
const obj = { a: 1, b: 2, c: 3 };
filter(obj, item => item > 2);
// => [3]
// Using a partial object
const obj = {
a: { id: 1, name: 'Alice' },
b: { id: 2, name: 'Bob' },
};
filter(obj, { name: 'Bob' });
// => [{ id: 2, name: 'Bob' }]
// Using a property-value pair
const obj = {
alice: { id: 1, name: 'Alice' },
bob: { id: 2, name: 'Bob' },
};
filter(obj, ['name', 'Alice']);
// => [{ id: 1, name: 'Alice' }]
// Using a property name
const obj = {
a: { id: 1, name: 'Alice' },
b: { id: 2, name: 'Bob' },
c: { id: 3, age: 28 },
};
filter(obj, 'name');
// => [{ id: 1, name: 'Alice' }, { id: 2, name: 'Bob' }]