Do not recompute states unless necessary

This commit is contained in:
Dan Abramov 2015-09-27 17:02:32 +03:00
parent a5dd802547
commit b5292609da

View File

@ -95,6 +95,7 @@ function liftReducer(reducer, initialState) {
* Manages how the DevTools actions modify the DevTools state. * Manages how the DevTools actions modify the DevTools state.
*/ */
return function liftedReducer(liftedState = initialLiftedState, liftedAction) { return function liftedReducer(liftedState = initialLiftedState, liftedAction) {
let shouldRecomputeStates = true;
let { let {
committedState, committedState,
stagedActions, stagedActions,
@ -131,6 +132,8 @@ function liftReducer(reducer, initialState) {
break; break;
case ActionTypes.JUMP_TO_STATE: case ActionTypes.JUMP_TO_STATE:
currentStateIndex = liftedAction.index; currentStateIndex = liftedAction.index;
// Optimization: we know the history has not changed.
shouldRecomputeStates = false;
break; break;
case ActionTypes.SWEEP: case ActionTypes.SWEEP:
stagedActions = stagedActions.filter((_, i) => !skippedActions[i]); stagedActions = stagedActions.filter((_, i) => !skippedActions[i]);
@ -142,8 +145,21 @@ function liftReducer(reducer, initialState) {
if (currentStateIndex === stagedActions.length - 1) { if (currentStateIndex === stagedActions.length - 1) {
currentStateIndex++; currentStateIndex++;
} }
stagedActions = [...stagedActions, liftedAction.action]; stagedActions = [...stagedActions, liftedAction.action];
timestamps = [...timestamps, liftedAction.timestamp]; timestamps = [...timestamps, liftedAction.timestamp];
// Optimization: we know that the past has not changed.
shouldRecomputeStates = false;
// Instead of recomputing the states, append the next one.
const previousEntry = computedStates[computedStates.length - 1];
const nextEntry = computeNextEntry(
reducer,
liftedAction.action,
previousEntry.state,
previousEntry.error
);
computedStates = [...computedStates, nextEntry];
break; break;
case ActionTypes.SET_MONITOR_STATE: case ActionTypes.SET_MONITOR_STATE:
monitorState = liftedAction.monitorState; monitorState = liftedAction.monitorState;
@ -159,12 +175,14 @@ function liftReducer(reducer, initialState) {
break; break;
} }
computedStates = recomputeStates( if (shouldRecomputeStates) {
reducer, computedStates = recomputeStates(
committedState, reducer,
stagedActions, committedState,
skippedActions stagedActions,
); skippedActions
);
}
return { return {
committedState, committedState,