Run results for: Immutability comparison

Test name	Executions per second
✓ manual immutable (no lib)	29,095 Ops/sec
Proxy	24,803 Ops/sec
Immerjs + reference check	19,229 Ops/sec
mutation + equal	14,591 Ops/sec
deepClone + deepEqual	1,365 Ops/sec

mutation + equal

// Create realistic Onyx state (30 keys, 5 levels, 300 items)
const createRealisticState = () => ({
  user: {
    accountID: 12345,
    profile: {
      personal: {
        details: {
          info: {
            name: 'John Doe',
            age: 30,
            email: 'john@example.com'
          }
        }
      }
    }
  },
  reports: Array.from({ length: 300 }, (_, i) => ({
    reportID: `r${i}`,
    name: `Report ${i}`,
    participants: [1, 2, 3],
    lastMessage: {
      text: 'Hello',
      timestamp: Date.now()
    }
  })),
  transactions: Array.from({ length: 300 }, (_, i) => ({
    transactionID: `t${i}`,
    amount: Math.random() * 1000,
    currency: 'USD'
  })),
  policy: {
    settings: {
      approval: {
        rules: {
          level1: { amount: 100 },
          level2: { amount: 500 }
        }
      }
    }
  }
});

// ShallowEqual implementation (like Onyx uses)
function shallowEqual(a, b) {
  if (a === b) return true;
  if (!a || !b) return false;
  if (typeof a !== 'object' || typeof b !== 'object') return a === b;
  
  const keysA = Object.keys(a);
  const keysB = Object.keys(b);
  
  if (keysA.length !== keysB.length) return false;
  
  for (let i = 0; i < keysA.length; i++) {
    if (a[keysA[i]] !== b[keysA[i]]) return false;
  }
  
  return true;
}

// Store before state
const beforeState = createRealisticState();
const prevValue = beforeState;

// Mutate (simulate merge/set)
const afterState = createRealisticState();
afterState.user.profile.personal.details.info.age = 31;
afterState.reports[0].name = 'Modified Report';
afterState.policy.settings.approval.rules.level1.amount = 200;

// Check for changes (what useOnyx does)
const hasChanged = !shallowEqual(prevValue, afterState);

Immerjs + reference check

const createRealisticState = () => ({
  user: {
    accountID: 12345,
    profile: {
      personal: {
        details: {
          info: {
            name: 'John Doe',
            age: 30,
            email: 'john@example.com'
          }
        }
      }
    }
  },
  reports: Array.from({ length: 300 }, (_, i) => ({
    reportID: `r${i}`,
    name: `Report ${i}`,
    participants: [1, 2, 3],
    lastMessage: {
      text: 'Hello',
      timestamp: Date.now()
    }
  })),
  transactions: Array.from({ length: 300 }, (_, i) => ({
    transactionID: `t${i}`,
    amount: Math.random() * 1000,
    currency: 'USD'
  })),
  policy: {
    settings: {
      approval: {
        rules: {
          level1: { amount: 100 },
          level2: { amount: 500 }
        }
      }
    }
  }
});

const originalState = createRealisticState();

// Create new immutable state with Immer
const newState = immer.produce(originalState, draft => {
  draft.user.profile.personal.details.info.age = 31;
  draft.reports[0].name = 'Modified Report';
  draft.policy.settings.approval.rules.level1.amount = 200;
});

// Fast reference equality check
const hasChanged = originalState !== newState;
const userChanged = originalState.user !== newState.user;
const reportsChanged = originalState.reports !== newState.reports;

// This is what useOnyx would do - just check if reference changed
const shouldUpdate = hasChanged;

manual immutable (no lib)

const createRealisticState = () => ({
  user: {
    accountID: 12345,
    profile: {
      personal: {
        details: {
          info: {
            name: 'John Doe',
            age: 30,
            email: 'john@example.com'
          }
        }
      }
    }
  },
  reports: Array.from({ length: 300 }, (_, i) => ({
    reportID: `r${i}`,
    name: `Report ${i}`,
    participants: [1, 2, 3],
    lastMessage: {
      text: 'Hello',
      timestamp: Date.now()
    }
  })),
  transactions: Array.from({ length: 300 }, (_, i) => ({
    transactionID: `t${i}`,
    amount: Math.random() * 1000,
    currency: 'USD'
  })),
  policy: {
    settings: {
      approval: {
        rules: {
          level1: { amount: 100 },
          level2: { amount: 500 }
        }
      }
    }
  }
});

const originalState = createRealisticState();

// Manual immutable updates - only recreate changed paths
const newState = {
  ...originalState,
  user: {
    ...originalState.user,
    profile: {
      ...originalState.user.profile,
      personal: {
        ...originalState.user.profile.personal,
        details: {
          ...originalState.user.profile.personal.details,
          info: {
            ...originalState.user.profile.personal.details.info,
            age: 31
          }
        }
      }
    }
  },
  reports: [
    { ...originalState.reports[0], name: 'Modified Report' },
    ...originalState.reports.slice(1)
  ],
  policy: {
    ...originalState.policy,
    settings: {
      ...originalState.policy.settings,
      approval: {
        ...originalState.policy.settings.approval,
        rules: {
          ...originalState.policy.settings.approval.rules,
          level1: {
            ...originalState.policy.settings.approval.rules.level1,
            amount: 200
          }
        }
      }
    }
  }
};

// Fast reference equality check
const hasChanged = originalState !== newState;

Proxy

const createRealisticState = () => ({
  user: {
    accountID: 12345,
    profile: {
      personal: {
        details: {
          info: {
            name: 'John Doe',
            age: 30,
            email: 'john@example.com'
          }
        }
      }
    }
  },
  reports: Array.from({ length: 300 }, (_, i) => ({
    reportID: `r${i}`,
    name: `Report ${i}`,
    participants: [1, 2, 3],
    lastMessage: {
      text: 'Hello',
      timestamp: Date.now()
    }
  })),
  transactions: Array.from({ length: 300 }, (_, i) => ({
    transactionID: `t${i}`,
    amount: Math.random() * 1000,
    currency: 'USD'
  })),
  policy: {
    settings: {
      approval: {
        rules: {
          level1: { amount: 100 },
          level2: { amount: 500 }
        }
      }
    }
  }
});

// Create Proxy with change tracking
function createChangeTrackingProxy(obj, pathPrefix = '') {
  let isDirty = false;
  const metadata = { isDirty: () => isDirty };
  
  function makeProxy(target, path) {
    return new Proxy(target, {
      set(obj, prop, value) {
        if (obj[prop] !== value) {
          isDirty = true;
        }
        obj[prop] = value;
        return true;
      },
      get(obj, prop) {
        if (prop === '__metadata__') return metadata;
        
        const value = obj[prop];
        if (value && typeof value === 'object' && !Array.isArray(value)) {
          return makeProxy(value, `${path}.${prop}`);
        }
        return value;
      }
    });
  }
  
  return makeProxy(obj, pathPrefix);
}

const state = createChangeTrackingProxy(createRealisticState());

// Mutate through proxy
state.user.profile.personal.details.info.age = 31;
state.reports[0].name = 'Modified Report';
state.policy.settings.approval.rules.level1.amount = 200;

// Check if dirty
const hasChanged = state.__metadata__.isDirty();

deepClone + deepEqual

const fastEquals = window['fast-equals'];

const createRealisticState = () => ({
  user: {
    accountID: 12345,
    profile: {
      personal: {
        details: {
          info: {
            name: 'John Doe',
            age: 30,
            email: 'john@example.com'
          }
        }
      }
    }
  },
  reports: Array.from({ length: 300 }, (_, i) => ({
    reportID: `r${i}`,
    name: `Report ${i}`,
    participants: [1, 2, 3],
    lastMessage: {
      text: 'Hello',
      timestamp: Date.now()
    }
  })),
  transactions: Array.from({ length: 300 }, (_, i) => ({
    transactionID: `t${i}`,
    amount: Math.random() * 1000,
    currency: 'USD'
  })),
  policy: {
    settings: {
      approval: {
        rules: {
          level1: { amount: 100 },
          level2: { amount: 500 }
        }
      }
    }
  }
});

// Store deep clone of before state
const beforeState = JSON.parse(JSON.stringify(createRealisticState()));

// Mutate
const afterState = createRealisticState();
afterState.user.profile.personal.details.info.age = 31;
afterState.reports[0].name = 'Modified Report';
afterState.policy.settings.approval.rules.level1.amount = 200;

// Deep equality check
const hasChanged = !fastEquals.deepEqual(beforeState, afterState);

Onyx fast merge

// Onyx merge utilities
const ONYX_INTERNALS__REPLACE_OBJECT_MARK = 'ONYX_INTERNALS__REPLACE_OBJECT_MARK';

function isMergeableObject(value) {
    const isNonNullObject = value != null ? typeof value === 'object' : false;
    return isNonNullObject && !(value instanceof RegExp) && !(value instanceof Date) && !Array.isArray(value);
}

function mergeObject(target, source, options, metadata, basePath) {
    const destination = {};
    const targetObject = isMergeableObject(target) ? target : undefined;

    if (targetObject) {
        Object.keys(targetObject).forEach((key) => {
            const targetProperty = targetObject?.[key];
            const sourceProperty = source?.[key];
            const shouldOmitNullishProperty = options.shouldRemoveNestedNulls && (targetProperty === null || sourceProperty === null);

            if (targetProperty === undefined || shouldOmitNullishProperty) {
                return;
            }
            destination[key] = targetProperty;
        });
    }

    Object.keys(source).forEach((key) => {
        let targetProperty = targetObject?.[key];
        const sourceProperty = source?.[key];
        const shouldOmitNullishProperty = options.shouldRemoveNestedNulls && sourceProperty === null;

        if (sourceProperty === undefined || shouldOmitNullishProperty) {
            return;
        }

        if (!isMergeableObject(sourceProperty)) {
            destination[key] = sourceProperty;
            return;
        }

        if (options.objectRemovalMode === 'mark' && targetProperty === null) {
            targetProperty = {[ONYX_INTERNALS__REPLACE_OBJECT_MARK]: true};
            metadata.replaceNullPatches.push([[...basePath, key], {...sourceProperty}]);
        }

        if (options.objectRemovalMode === 'replace' && sourceProperty[ONYX_INTERNALS__REPLACE_OBJECT_MARK]) {
            const sourcePropertyWithoutMark = {...sourceProperty};
            delete sourcePropertyWithoutMark.ONYX_INTERNALS__REPLACE_OBJECT_MARK;
            destination[key] = sourcePropertyWithoutMark;
            return;
        }

        destination[key] = fastMerge(targetProperty, sourceProperty, options, metadata, [...basePath, key]).result;
    });

    return destination;
}

function fastMerge(target, source, options, metadata, basePath = []) {
    if (!metadata) {
        metadata = { replaceNullPatches: [] };
    }

    if (Array.isArray(source) || source === null || source === undefined) {
        return {result: source, replaceNullPatches: metadata.replaceNullPatches};
    }

    const optionsWithDefaults = {
        shouldRemoveNestedNulls: options?.shouldRemoveNestedNulls ?? false,
        objectRemovalMode: options?.objectRemovalMode ?? 'none',
    };

    const mergedValue = mergeObject(target, source, optionsWithDefaults, metadata, basePath);
    return {result: mergedValue, replaceNullPatches: metadata.replaceNullPatches};
}

function shallowEqual(a, b) {
    if (a === b) return true;
    if (!a || !b) return false;
    if (typeof a !== 'object' || typeof b !== 'object') return a === b;
    
    const keysA = Object.keys(a);
    const keysB = Object.keys(b);
    
    if (keysA.length !== keysB.length) return false;
    
    for (let i = 0; i < keysA.length; i++) {
        if (a[keysA[i]] !== b[keysA[i]]) return false;
    }
    
    return true;
}

const createRealisticState = () => ({
    user: {
        accountID: 12345,
        profile: {
            personal: {
                details: {
                    info: {
                        name: 'John Doe',
                        age: 30,
                        email: 'john@example.com'
                    }
                }
            }
        }
    },
    reports: Array.from({ length: 300 }, (_, i) => ({
        reportID: `r${i}`,
        name: `Report ${i}`,
        participants: [1, 2, 3],
        lastMessage: {
            text: 'Hello',
            timestamp: Date.now()
        }
    })),
    transactions: Array.from({ length: 300 }, (_, i) => ({
        transactionID: `t${i}`,
        amount: Math.random() * 1000,
        currency: 'USD'
    })),
    policy: {
        settings: {
            approval: {
                rules: {
                    level1: { amount: 100 },
                    level2: { amount: 500 }
                }
            }
        }
    }
});

// Simulate what Onyx does: merge updates into existing state
const originalState = createRealisticState();

// Updates to merge (like what comes from Onyx.merge)
const updates = {
    user: {
        profile: {
            personal: {
                details: {
                    info: {
                        age: 31
                    }
                }
            }
        }
    },
    reports: [
        { reportID: 'r0', name: 'Modified Report', participants: [1, 2, 3], lastMessage: { text: 'Hello', timestamp: Date.now() } }
    ],
    policy: {
        settings: {
            approval: {
                rules: {
                    level1: { amount: 200 }
                }
            }
        }
    }
};

// Merge using Onyx fastMerge
const mergeResult = fastMerge(originalState, updates);
const newState = mergeResult.result;

// Check for changes using shallowEqual (what useOnyx does)
const hasChanged = !shallowEqual(originalState, newState);
const userChanged = !shallowEqual(originalState.user, newState.user);
const reportsChanged = !shallowEqual(originalState.reports, newState.reports);

Run results for: Immutability comparison

immerjs, Proxy, fastMerge, deepEqual

mutation + equal

Immerjs + reference check

manual immutable (no lib)

Proxy

deepClone + deepEqual

Onyx fast merge