withDiff • tldraw Docs

When writing incrementally-computed signals it is convenient (and usually more performant) to incrementally compute the diff too.

You can use this function to wrap the return value of a computed signal function to indicate that the diff should be used instead of calculating a new one with AtomOptions.computeDiff.

function withDiff<Value, Diff>(value: Value, diff: Diff): WithDiff<Value, Diff>;

Example

const count = atom("count", 0);
const double = computed(
  "double",
  (prevValue) => {
    const nextValue = count.get() * 2;
    if (isUninitialized(prevValue)) {
      return nextValue;
    }
    return withDiff(nextValue, nextValue - prevValue);
  },
  { historyLength: 10 },
);

Parameters

Name	Description
`value`	`Value;` The value.
`diff`	`Diff;` The diff.

Returns

WithDiff<Value, Diff>;