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minor optimization to diff-arrays

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This commit is contained in:
Hazelnoot 2025-05-25 12:33:05 -04:00
parent 6b3ddc6768
commit 8a2ed3bc86
2 changed files with 7 additions and 5 deletions
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6
packages/backend/src/misc/diff-arrays.ts
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@ -10,8 +10,9 @@ export interface DiffResult<T> {
/**
* Calculates the difference between two snapshots of data.
* Null, undefined, and empty arrays are supported, and values do not have to be unique.
* Null, undefined, and empty arrays are supported, and duplicate values are ignored.
* Result sets are de-duplicated, and will be empty if no data was added or removed (respectively).
* The inputs are treated as un-ordered, so a re-ordering of the same data will NOT be considered a change.
* @param dataBefore Array containing data before the change
* @param dataAfter Array containing data after the change
*/
@ -26,7 +27,8 @@ export function diffArrays<T>(dataBefore: T[] | null | undefined, dataAfter: T[]
for (const host of before) {
// before and NOT after => removed
if (!after.has(host)) {
// delete operation removes duplicates to speed up the "after" loop
if (!after.delete(host)) {
removed.push(host);
}
}

6
packages/backend/test/unit/misc/diff-arrays.ts
View file

@ -18,19 +18,19 @@ describe(diffArrays, () => {
expect(result.removed).toHaveLength(0);
});
it('should remove before when added is empty', () => {
it('should remove before when after is empty', () => {
const result = diffArrays([1, 2, 3], []);
expect(result.added).toHaveLength(0);
expect(result.removed).toEqual([1, 2, 3]);
});
it('should deduplicate before when added is empty', () => {
it('should deduplicate before when after is empty', () => {
const result = diffArrays([1, 1, 2, 2, 3], []);
expect(result.added).toHaveLength(0);
expect(result.removed).toEqual([1, 2, 3]);
});
it('should remove after when before is empty', () => {
it('should add after when before is empty', () => {
const result = diffArrays([], [1, 2, 3]);
expect(result.added).toEqual([1, 2, 3]);
expect(result.removed).toHaveLength(0);