Type Editor

---

Type Editor / @type-editor/model / diff/find-diff-start / findDiffStart

Function: findDiffStart()

function findDiffStart(a, b, pos): number;

Defined in: packages/model/src/diff/find-diff-start.ts:46

Find the first position at which two fragments differ.

This function performs a deep comparison of two fragments, starting from the beginning and moving forward until it finds the first difference. It compares nodes recursively, checking:

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

The comparison is optimized to skip identical subtrees by checking reference equality first. For text nodes, it performs character-by-character comparison to find the exact position where the text diverges.

Parameters

Parameter	Type	Description
a	Fragment	The first fragment to compare.
b	Fragment	The second fragment to compare.
pos	number	The starting position offset in the document. This is used to calculate absolute positions in the document tree. Should typically start at 0 for top-level comparisons.

Returns

number

The position where the fragments first differ, or null if the fragments are identical. The position is relative to the start of fragment a and accounts for the initial pos offset.

Example

const diff = findDiffStart(oldFragment, newFragment, 0);
if (diff !== null) {
  console.log(`Fragments differ at position ${diff}`);
} else {
  console.log("Fragments are identical");
}