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Function: diff()

Call Signature​

diff<T, TId>(oldItems, newItems, getId, isEqual?): DiffResult<T>

Defined in: collection/diff/index.ts:45

Compares two collections and returns added, updated, removed, and unchanged items.

Useful for syncing data, detecting changes, and implementing optimistic updates.

Type Parameters​

T​

T

TId​

TId extends string | number

Parameters​

oldItems​

readonly T[]

The original collection

newItems​

readonly T[]

The updated collection

getId​

(item) => TId

Function to extract unique identifier

isEqual?​

Comparator<T>

Optional custom equality checker (defaults to deep equality)

Returns​

DiffResult<T>

A DiffResult containing categorized changes

Example​

// Data-first
const oldUsers = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
]
const newUsers = [
  { id: 1, name: 'Alicia' }, // updated
  { id: 3, name: 'Charlie' }  // added
]

diff(oldUsers, newUsers, (u) => u.id)
// => {
//   added: [{ id: 3, name: 'Charlie' }],
//   updated: [{ old: { id: 1, name: 'Alice' }, new: { id: 1, name: 'Alicia' } }],
//   removed: [{ id: 2, name: 'Bob' }],
//   unchanged: []
// }

// Data-last (in pipe)
pipe(
  oldUsers,
  diff(newUsers, (u) => u.id)
)

See​

  • union - for merging collections
  • intersect - for finding common elements

Call Signature​

diff<T, TId>(newItems, getId, isEqual?): (oldItems) => DiffResult<T>

Defined in: collection/diff/index.ts:51

Compares two collections and returns added, updated, removed, and unchanged items.

Useful for syncing data, detecting changes, and implementing optimistic updates.

Type Parameters​

T​

T

TId​

TId extends string | number

Parameters​

newItems​

readonly T[]

The updated collection

getId​

(item) => TId

Function to extract unique identifier

isEqual?​

Comparator<T>

Optional custom equality checker (defaults to deep equality)

Returns​

A DiffResult containing categorized changes

(oldItems): DiffResult<T>

Parameters​

oldItems​

readonly T[]

Returns​

DiffResult<T>

Example​

// Data-first
const oldUsers = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
]
const newUsers = [
  { id: 1, name: 'Alicia' }, // updated
  { id: 3, name: 'Charlie' }  // added
]

diff(oldUsers, newUsers, (u) => u.id)
// => {
//   added: [{ id: 3, name: 'Charlie' }],
//   updated: [{ old: { id: 1, name: 'Alice' }, new: { id: 1, name: 'Alicia' } }],
//   removed: [{ id: 2, name: 'Bob' }],
//   unchanged: []
// }

// Data-last (in pipe)
pipe(
  oldUsers,
  diff(newUsers, (u) => u.id)
)

See​

  • union - for merging collections
  • intersect - for finding common elements