improve performance of strict copies

Author: planttheidea

README.md

@@ -311,7 +311,7 @@ _Small number of properties, all values are primitives_
 | fast-clone         | 1,635,636           |
 | ramda              | 1,143,794           |
 | deepclone          | 1,253,298           |
-| fast-copy (strict) | 1,007,193           |
+| fast-copy (strict) | 1,161,882           |
 
 #### Complex objects
 
@@ -324,8 +324,8 @@ _Large number of properties, values are a combination of primitives and complex
 | fast-clone         | 99,246              |
 | clone              | 82,487              |
 | ramda              | 78,805              |
+| fast-copy (strict) | 70,160              |
 | lodash.cloneDeep   | 66,068              |
-| fast-copy (strict) | 65,617              |
 
 #### Big data
 
@@ -337,8 +337,8 @@ _Very large number of properties with high amount of nesting, mainly objects and
 | fast-clone         | 265                 |
 | lodash.cloneDeep   | 165                 |
 | deepclone          | 149                 |
+| fast-copy (strict) | 133                 |
 | clone              | 122                 |
-| fast-copy (strict) | 120                 |
 | ramda              | 39                  |
 
 #### Circular objects
@@ -351,7 +351,7 @@ _Objects that deeply reference themselves_
 | deepclone          | 1,285,548           |
 | lodash.cloneDeep   | 1,104,529           |
 | clone              | 1,103,213           |
-| fast-copy (strict) | 757,758             |
+| fast-copy (strict) | 1,028,220           |
 | ramda              | 388,033             |
 | fast-clone         | 0 (not supported)   |
 
@@ -367,7 +367,7 @@ _Custom constructors, React components, etc_
 | fast-clone         | 58,831              |
 | deepclone          | 25,780              |
 | ramda              | 25,309              |
-| fast-copy (strict) | 17,766              |
+| fast-copy (strict) | 20,480              |
 
 ## Development
 

eslint.config.js

@@ -25,6 +25,7 @@ export default defineConfig([
         'error',
         { argsIgnorePattern: '^_', varsIgnorePattern: '^_' },
       ],
+      '@typescript-eslint/prefer-for-of': 'off',
       '@typescript-eslint/unbound-method': 'off',
     },
     settings: {

src/copier.ts

@@ -11,51 +11,42 @@ export interface State {
   prototype: any;
 }
 
-const {
-  defineProperty,
-  getOwnPropertyDescriptor,
-  getOwnPropertyNames,
-  getOwnPropertySymbols,
-} = Object;
 const { hasOwnProperty, propertyIsEnumerable } = Object.prototype;
 
-const SUPPORTS_SYMBOL = typeof getOwnPropertySymbols === 'function';
-
-function getStrictPropertiesModern(object: any): Array<string | symbol> {
-  return (getOwnPropertyNames(object) as Array<string | symbol>).concat(
-    getOwnPropertySymbols(object),
-  );
-}
-
 /**
  * Get the properites used when copying objects strictly. This includes both keys and symbols.
  */
-const getStrictProperties = SUPPORTS_SYMBOL
-  ? getStrictPropertiesModern
-  : getOwnPropertyNames;
+const getStrictProperties = ((getNames, getSymbols) => {
+  if (typeof getSymbols === 'function') {
+    return (object: object): Array<string | symbol> => {
+      const names = getNames(object) as Array<string | symbol>;
+      const symbols = getSymbols(object);
+
+      return symbols.length ? names.concat(symbols) : names;
+    };
+  }
+
+  return getNames;
+})(Object.getOwnPropertyNames, Object.getOwnPropertySymbols);
 
 /**
  * Striclty copy all properties contained on the object.
  */
-function copyOwnPropertiesStrict<Value>(
+function copyOwnPropertiesStrict<Value extends object>(
   value: Value,
   clone: Value,
   state: State,
 ): Value {
   const properties = getStrictProperties(value);
 
-  for (
-    let index = 0, length = properties.length, property, descriptor;
-    index < length;
-    ++index
-  ) {
-    property = properties[index];
+  for (let index = 0; index < properties.length; ++index) {
+    const property = properties[index];
 
     if (property === 'callee' || property === 'caller') {
       continue;
     }
 
-    descriptor = getOwnPropertyDescriptor(value, property);
+    const descriptor = Object.getOwnPropertyDescriptor(value, property);
 
     if (!descriptor) {
       // In extra edge cases where the property descriptor cannot be retrived, fall back to
@@ -70,7 +61,7 @@ function copyOwnPropertiesStrict<Value>(
     }
 
     try {
-      defineProperty(clone, property, descriptor);
+      Object.defineProperty(clone, property, descriptor);
     } catch {
       // Tee above can fail on node in edge cases, so fall back to the loose assignment.
       (clone as any)[property] = descriptor.value;
@@ -89,7 +80,7 @@ export function copyArrayLoose(array: any[], state: State) {
   // set in the cache immediately to be able to reuse the object recursively
   state.cache.set(array, clone);
 
-  for (let index = 0, length = array.length; index < length; ++index) {
+  for (let index = 0; index < array.length; ++index) {
     clone[index] = state.copier(array[index], state);
   }
 
@@ -177,62 +168,58 @@ export function copyMapStrict<Value extends Map<any, any>>(
   return copyOwnPropertiesStrict(map, copyMapLoose(map, state), state);
 }
 
-function copyObjectLooseLegacy<Value extends Record<string, any>>(
-  object: Value,
-  state: State,
-): Value {
-  const clone: any = getCleanClone(state.prototype);
-
-  // set in the cache immediately to be able to reuse the object recursively
-  state.cache.set(object, clone);
-
-  for (const key in object) {
-    if (hasOwnProperty.call(object, key)) {
-      clone[key] = state.copier(object[key], state);
-    }
-  }
-
-  return clone;
-}
-
-function copyObjectLooseModern<Value extends Record<string, any>>(
-  object: Value,
-  state: State,
-): Value {
-  const clone = getCleanClone(state.prototype);
-
-  // set in the cache immediately to be able to reuse the object recursively
-  state.cache.set(object, clone);
-
-  for (const key in object) {
-    if (hasOwnProperty.call(object, key)) {
-      clone[key] = state.copier(object[key], state);
-    }
+/**
+ * Deeply copy the properties (keys and symbols) and values of the original.
+ */
+export const copyObjectLoose = ((getSymbols) => {
+  if (typeof getSymbols === 'function') {
+    return <Value extends Record<string, any>>(
+      object: Value,
+      state: State,
+    ): Value => {
+      const clone = getCleanClone(state.prototype);
+
+      // set in the cache immediately to be able to reuse the object recursively
+      state.cache.set(object, clone);
+
+      for (const key in object) {
+        if (hasOwnProperty.call(object, key)) {
+          clone[key] = state.copier(object[key], state);
+        }
+      }
+
+      const symbols = getSymbols(object);
+
+      for (let index = 0; index < symbols.length; ++index) {
+        const symbol = symbols[index];
+
+        if (propertyIsEnumerable.call(object, symbol)) {
+          clone[symbol] = state.copier((object as any)[symbol], state);
+        }
+      }
+
+      return clone;
+    };
   }
 
-  const symbols = getOwnPropertySymbols(object);
+  return <Value extends Record<string, any>>(
+    object: Value,
+    state: State,
+  ): Value => {
+    const clone: any = getCleanClone(state.prototype);
 
-  for (
-    let index = 0, length = symbols.length, symbol;
-    index < length;
-    ++index
-  ) {
-    symbol = symbols[index];
+    // set in the cache immediately to be able to reuse the object recursively
+    state.cache.set(object, clone);
 
-    if (propertyIsEnumerable.call(object, symbol)) {
-      clone[symbol] = state.copier((object as any)[symbol], state);
+    for (const key in object) {
+      if (hasOwnProperty.call(object, key)) {
+        clone[key] = state.copier(object[key], state);
+      }
     }
-  }
 
-  return clone;
-}
-
-/**
- * Deeply copy the properties (keys and symbols) and values of the original.
- */
-export const copyObjectLoose = SUPPORTS_SYMBOL
-  ? copyObjectLooseModern
-  : copyObjectLooseLegacy;
+    return clone;
+  };
+})(Object.getOwnPropertySymbols);
 
 /**
  * Deeply copy the properties (keys and symbols) and values of the original, as well

src/index.ts

@@ -21,8 +21,6 @@ import type { InternalCopier, State } from './copier';
 
 export type { State } from './copier';
 
-const { isArray } = Array;
-const { assign } = Object;
 // Handling extremely old environments without Object.getPrototypeOf.
 // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
 const getPrototypeOf = Object.getPrototypeOf || ((obj) => obj.__proto__);
@@ -52,7 +50,7 @@ const DEFAULT_LOOSE_OPTIONS: Required<CreateCopierOptions> = {
   regExp: copyRegExp,
   set: copySetLoose,
 };
-const DEFAULT_STRICT_OPTIONS: Required<CreateCopierOptions> = assign(
+const DEFAULT_STRICT_OPTIONS: Required<CreateCopierOptions> = Object.assign(
   {},
   DEFAULT_LOOSE_OPTIONS,
   {
@@ -104,7 +102,7 @@ function getTagSpecificCopiers(
  * Create a custom copier based on the object-specific copy methods passed.
  */
 export function createCopier(options: CreateCopierOptions) {
-  const normalizedOptions = assign({}, DEFAULT_LOOSE_OPTIONS, options);
+  const normalizedOptions = Object.assign({}, DEFAULT_LOOSE_OPTIONS, options);
   const tagSpecificCopiers = getTagSpecificCopiers(normalizedOptions);
 
   if (!tagSpecificCopiers.Object || !tagSpecificCopiers.Array) {
@@ -136,7 +134,7 @@ export function createCopier(options: CreateCopierOptions) {
     }
 
     // arrays
-    if (isArray(value)) {
+    if (Array.isArray(value)) {
       return copyArray(value, state);
     }
 
@@ -164,7 +162,7 @@ export function createCopier(options: CreateCopierOptions) {
  * same internals as `copyStrict`.
  */
 export function createStrictCopier(options: CreateCopierOptions) {
-  return createCopier(assign({}, DEFAULT_STRICT_OPTIONS, options));
+  return createCopier(Object.assign({}, DEFAULT_STRICT_OPTIONS, options));
 }
 
 /**