Find Missing Elements

findMissingElements

Performs a deep comparison between two arrays and returns elements missing from one array relative to the other. It allows you to specify the direction of comparison to extract missing values from either array.

Function Signature

function findMissingElements<T, U>(
  array1: T[],
  array2: U[],
  missingFrom: 'from-first' | 'from-second'
): (T | U)[]

Parameters

Parameter	Type	Description
`array1`	`T[]`	First array to compare
`array2`	`U[]`	Second array to compare
`missingFrom`	`'from-first' \| 'from-second'`	Direction of comparison: - `'from-first'`: Finds elements in `array1` missing from `array2` - `'from-second'`: Finds elements in `array2` missing from `array1`

Returns

(T | U)[]: An array containing elements present in the source array but missing in the target array (based on deep equality comparison).

Example Usage

playground.ts

Notes

Performs deep equality comparison (handles objects and nested structures) using isDeepEqual.
Preserves original element references.
Returns empty array if no differences found.
Works with arrays of different types (T and U).

Comparison Logic

'from-first' mode:

array1.filter(item => !array2.some(item2 => isDeepEqual(item, item2)))

'from-second' mode:

array2.filter(item => !array1.some(item1 => isDeepEqual(item, item1)))