Type Editor

---

Type Editor / @type-editor/model / diff/find-diff-end / findDiffEnd

Function: findDiffEnd()

function findDiffEnd(a, b, posA, posB): DiffPosition;

Defined in: packages/model/src/diff/find-diff-end.ts:76

Find the last position at which two fragments differ.

This function performs a deep comparison of two fragments, starting from the end and moving backward until it finds the last difference. It's the complement to findDiffStart and is used together with it to determine the exact range of changes between two document states.

The function compares nodes in reverse order, checking:

• Reference equality (same node object)
• Markup equality (same type and attributes)
• Text content character-by-character from the end for text nodes
• Child content recursively for container nodes

Like findDiffStart, this function is optimized to skip identical subtrees by checking reference equality first. For text nodes, it performs reverse character-by-character comparison to find the exact position where the text diverges from the end.

Parameters

Parameter	Type	Description
a	Fragment	The first fragment to compare.
b	Fragment	The second fragment to compare.
posA	number	The ending position in fragment a. This should typically be the size of fragment a minus 1 for top-level comparisons. The function counts backwards from this position.
posB	number	The ending position in fragment b. This should typically be the size of fragment b minus 1 for top-level comparisons. The function counts backwards from this position.

Returns

DiffPosition

A DiffPosition object containing the positions where the fragments last differ (selfPos in fragment a and otherPos in fragment b), or null if the fragments are identical. The positions indicate the end boundary of the differing region.

Examples

const diffEnd = findDiffEnd(
  oldFragment,
  newFragment,
  oldFragment.size,
  newFragment.size,
);
if (diffEnd !== null) {
  console.log(
    `Last difference at positions ${diffEnd.selfPos} and ${diffEnd.otherPos}`,
  );
} else {
  console.log("Fragments are identical");
}

// Finding the exact range of changes
const start = findDiffStart(oldFragment, newFragment, 0);
const end = findDiffEnd(
  oldFragment,
  newFragment,
  oldFragment.size,
  newFragment.size,
);
if (start !== null && end !== null) {
  console.log(`Changes span from ${start} to ${end.selfPos} in old fragment`);
  console.log(`Changes span from ${start} to ${end.otherPos} in new fragment`);
}