perf: improve performance by using loops

RebeccaStevens · Sep 16, 2021 · 38e4b7f · 38e4b7f
1 parent 440f219
commit 38e4b7f
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Showing 2 changed files with 61 additions and 41 deletions.
diff --git a/src/deepmerge.ts b/src/deepmerge.ts
@@ -117,43 +117,52 @@ function mergeUnknowns<
   U extends DeepMergeMergeFunctionUtils,
   MF extends DeepMergeMergeFunctionsURIs
 >(values: Ts, utils: U): DeepMergeHKT<Ts, MF> {
-  const types = values.map(getObjectType);
-  const type = types[0];
+  const type = getObjectType(values[0]);
 
-  if (types.every((value) => value === type)) {
-    if (type === ObjectType.RECORD) {
+  // eslint-disable-next-line functional/no-loop-statement, functional/no-let -- using a loop here is more performant than mapping every value and then testing every value.
+  for (let i = 1; i < values.length; i++) {
+    // eslint-disable-next-line functional/no-conditional-statement -- waiting on https://github.com/jonaskello/eslint-plugin-functional/issues/269
+    if (getObjectType(values[i]) === type) {
+      continue;
+    }
+
+    return utils.mergeFunctions.mergeOthers(values, utils) as DeepMergeHKT<
+      Ts,
+      MF
+    >;
+  }
+
+  switch (type) {
+    case ObjectType.RECORD:
       return utils.mergeFunctions.mergeRecords(
         values as ReadonlyArray<Readonly<Record<RecordProperty, unknown>>>,
         utils
       ) as DeepMergeHKT<Ts, MF>;
-    }
 
-    if (type === ObjectType.ARRAY) {
+    case ObjectType.ARRAY:
       return utils.mergeFunctions.mergeArrays(
         values as ReadonlyArray<ReadonlyArray<unknown>>,
         utils
       ) as DeepMergeHKT<Ts, MF>;
-    }
 
-    if (type === ObjectType.SET) {
+    case ObjectType.SET:
       return utils.mergeFunctions.mergeSets(
         values as ReadonlyArray<Readonly<ReadonlySet<unknown>>>,
         utils
       ) as DeepMergeHKT<Ts, MF>;
-    }
 
-    if (type === ObjectType.MAP) {
+    case ObjectType.MAP:
       return utils.mergeFunctions.mergeMaps(
         values as ReadonlyArray<Readonly<ReadonlyMap<unknown, unknown>>>,
         utils
       ) as DeepMergeHKT<Ts, MF>;
-    }
-  }
 
-  return utils.mergeFunctions.mergeOthers(values, utils) as DeepMergeHKT<
-    Ts,
-    MF
-  >;
+    default:
+      return utils.mergeFunctions.mergeOthers(values, utils) as DeepMergeHKT<
+        Ts,
+        MF
+      >;
+  }
 }
 
 /**
@@ -166,26 +175,34 @@ function mergeRecords<
   U extends DeepMergeMergeFunctionUtils,
   MF extends DeepMergeMergeFunctionsURIs
 >(values: Ts, utils: U) {
-  const neverValue = {};
-  return Object.fromEntries(
-    [...getKeys(values)]
-      .map((key) => {
-        const propValues = values
-          .map((value) =>
-            objectHasProperty(value, key) ? value[key] : neverValue
-          )
-          .filter((value) => value !== neverValue);
-
-        // assert(propValues.length > 0);
-
-        if (propValues.length === 1) {
-          return [key, propValues[0]];
-        }
-
-        return [key, mergeUnknowns(propValues, utils)];
-      })
-      .filter((value): value is [unknown, unknown] => value !== neverValue)
-  ) as DeepMergeRecordsDefaultHKT<Ts, MF>;
+  if (values.length === 1) {
+    return values[0] as DeepMergeRecordsDefaultHKT<Ts, MF>;
+  }
+
+  const result: Record<RecordProperty, unknown> = {};
+
+  /* eslint-disable functional/no-loop-statement, functional/no-conditional-statement -- using a loop here is more performant. */
+
+  for (const key of getKeys(values)) {
+    const propValues = [];
+
+    for (const value of values) {
+      if (objectHasProperty(value, key)) {
+        propValues.push(value[key]);
+      }
+    }
+
+    // assert(propValues.length > 0);
+
+    result[key] =
+      propValues.length === 1
+        ? propValues[0]
+        : mergeUnknowns(propValues, utils);
+  }
+
+  /* eslint-enable functional/no-loop-statement, functional/no-conditional-statement */
+
+  return result as DeepMergeRecordsDefaultHKT<Ts, MF>;
 }
 
 /**

diff --git a/src/utils.ts b/src/utils.ts
@@ -55,19 +55,22 @@ export function getObjectType(object: unknown): ObjectType {
 export function getKeys(
   objects: Readonly<ReadonlyArray<object>>
 ): Set<RecordProperty> {
-  return objects.reduce<Set<RecordProperty>>((mutableCarry, object) => {
-    // eslint-disable-next-line functional/no-loop-statement -- using a loop here is more efficient.
+  const keys = new Set<RecordProperty>();
+
+  /* eslint-disable functional/no-loop-statement -- using a loop here is more efficient. */
+  for (const object of objects) {
     for (const key of [
       ...Object.getOwnPropertyNames(object),
       ...Object.getOwnPropertySymbols(object),
     ].filter((property) =>
       Object.prototype.propertyIsEnumerable.call(object, property)
     )) {
-      mutableCarry.add(key);
+      keys.add(key);
     }
+  }
+  /* eslint-enable functional/no-loop-statement */
 
-    return mutableCarry;
-  }, new Set<RecordProperty>());
+  return keys;
 }
 
 /**