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diff/find-diff-end ​

Functions ​

FunctionDescription

findDiffEnd

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.

Examples

typescript
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");
}
typescript
// 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`);
}