object deep clone function

Author: FairlyTales

data_structures/deepClone.ts

@@ -0,0 +1,74 @@
+// function for object deep cloning
+// the main idea of deep cloning is to create a complete copy of an object whose
+// properties do not share the same references (point to the same underlying values)
+// as those of the source object from which the copy was made
+
+function deepClone(obj: any) {
+  if (obj === null) return null;
+
+  // create a shallow clone
+  let clone = Object.assign({}, obj);
+
+  // iterate though all keys and either assign a primitive if the value in the
+  // original object is a primitive or recursively call the clone function
+  // if the value is an object
+  Object.keys(clone).forEach((key) => (
+      clone[key] =
+        typeof obj[key] === 'object' ?
+          deepClone(obj[key]) :
+          obj[key]
+    ),
+  );
+
+  // if an object is an array set its length to that of the original and create
+  // a copy using Array.from method, if we don't do it the arrays will be just objects
+  if (Array.isArray(obj)) {
+    clone.length = obj.length;
+    return Array.from(clone);
+  }
+
+  return clone;
+}
+
+// ----------------------------------------------------------------------------
+// Tests
+// ----------------------------------------------------------------------------
+
+const originalObject = {
+  string: 'I am a sting',
+  array: [1, 2, 3, [4, 5, 6]],
+  innerObject: {
+    number: 1,
+    innerInnerObject: {
+      number: 2,
+      array: [4, 5, 6],
+    },
+  },
+};
+
+const deepClonedObject = deepClone(originalObject);
+const shallowClonedObject = Object.assign({}, originalObject);
+
+console.log('originalObject:');
+console.log(originalObject);
+console.log('deepClonedObject:');
+console.log(deepClonedObject);
+console.log('shallowClonedObject:');
+console.log(shallowClonedObject);
+
+// should be false
+console.log('Should be false: ');
+console.log(originalObject === deepClonedObject);
+
+// should be false
+console.log('Should be false: ');
+console.log(originalObject === shallowClonedObject);
+
+// should be false because deep clone houses the entire copied inner object, not just the pointer to an address
+console.log('Should be false: ');
+console.log(originalObject.innerObject === deepClonedObject.object);
+
+// should be true because shallow copy just stores a pointer to an address
+console.log('Should be true: ');
+console.log(originalObject.innerObject === shallowClonedObject.innerObject);
+