Improve(Extend): Support Symbol

Author: 1aron

packages/extend/src/index.ts

@@ -1,13 +1,13 @@
-function isSpecificValue(val) {
+function isSpecificValue(val: any): boolean {
     const _Buffer = typeof Buffer !== 'undefined' ? Buffer : null
     return (
-        _Buffer && val instanceof _Buffer
-        || val instanceof Date
-        || val instanceof RegExp
-    ) ? true : false
+        (_Buffer && val instanceof _Buffer) ||
+        val instanceof Date ||
+        val instanceof RegExp
+    )
 }
 
-function cloneSpecificValue(val) {
+function cloneSpecificValue(val: any): any {
     const _Buffer = typeof Buffer !== 'undefined' ? Buffer : null
     if (_Buffer && val instanceof Buffer) {
         const x = Buffer.alloc(val.length)
@@ -22,10 +22,7 @@ function cloneSpecificValue(val) {
     }
 }
 
-/**
- * Recursive cloning array.
- */
-function deepCloneArray(arr: any[]) {
+function deepCloneArray(arr: any[]): any[] {
     const clone = []
     arr.forEach(function (item, index) {
         if (typeof item === 'object' && item !== null) {
@@ -43,68 +40,44 @@ function deepCloneArray(arr: any[]) {
     return clone
 }
 
-function safeGetProperty(object, property) {
-    return property === '__proto__' ? undefined : object[property]
+function safeGetProperty(object: any, property: string | symbol): any {
+    if (property === '__proto__') return undefined
+    return Object.prototype.hasOwnProperty.call(object, property)
+        ? object[property]
+        : undefined
 }
 
-/**
- * Extening object that entered in first argument.
- *
- * Returns extended object or false if have no target object or incorrect type.
- *
- * If you wish to clone source object (without modify it), just use empty new
- * object as first argument, like this:
- *   extend({}, yourObj_1, [yourObj_N]);
- */
-export default function extend(...sources: any[]) {
-    const target = {}
-
-    let val: any, src: any
+export default function extend(...sources: any[]): any {
+    const target: any = {}
 
     sources.forEach(function (obj) {
-        // skip argument if isn't an object, is null, or is an array
         if (typeof obj !== 'object' || obj === null || Array.isArray(obj)) {
             return
         }
 
-        Object.keys(obj).forEach(function (key) {
-            src = safeGetProperty(target, key) // source value
-            val = safeGetProperty(obj, key) // new value
+        Reflect.ownKeys(obj).forEach(function (key) {
+            const src = safeGetProperty(target, key)
+            const val = safeGetProperty(obj, key)
 
-            // recursion prevention
             if (val === target) {
                 return
-
-                /**
-                 * if new value isn't object then just overwrite by new value
-                 * instead of extending.
-                 */
             } else if (typeof val !== 'object' || val === null) {
                 target[key] = val
-                return
-
-                // just clone arrays (and recursive clone objects inside)
             } else if (Array.isArray(val)) {
                 target[key] = deepCloneArray(val)
-                return
-
-                // custom cloning and overwrite for specific objects
             } else if (isSpecificValue(val)) {
                 target[key] = cloneSpecificValue(val)
-                return
-
-                // overwrite by new value if source isn't object or array
-            } else if (typeof src !== 'object' || src === null || Array.isArray(src)) {
+            } else if (
+                typeof src !== 'object' ||
+                src === null ||
+                Array.isArray(src)
+            ) {
                 target[key] = extend({}, val)
-                return
-
-                // source value and new value is objects both, extending...
             } else {
                 target[key] = extend(src, val)
-                return
             }
         })
     })
 
     return target
-}
+}

packages/extend/tests/test.ts

@@ -277,4 +277,27 @@ it('prevent source contamination', () => {
             }
         }
     })
+})
+
+test('symbol', ()=> {
+    const C = Symbol('c')
+    const D = Symbol('d')
+    const obj1 = {
+        a: 1,
+        b: 2,
+        [C]: 3
+    }
+    const obj2 = {
+        b: 3,
+        c: 4,
+        [D]: 5
+    }
+    const result = extend(obj1, obj2)
+    expect(result).toEqual({
+        a: 1,
+        b: 3,
+        c: 4,
+        [C]: 3,
+        [D]: 5
+    })
 })