Merge branch 'master' of github.com:travisjupp/Javascript

Author: travisjupp

shallowVSDeepCopy.js

@@ -0,0 +1,44 @@
+const originalObject = {
+  somePrimitive: 3,
+  someReference: {
+    someNestedPrim: 7,
+    someNestedRef: ["a", "b"]
+  },
+  anotherPrimitive: "hello" 
+};
+
+// Create a shallow copy using the spread syntax
+const shallowCopy = { ...originalObject };
+
+console.log("--- Initial State ---");
+console.log("Original Object:", JSON.stringify(originalObject));
+console.log("Shallow Copy:", JSON.stringify(shallowCopy));
+
+console.log("\n--- Modifying the shallow copy ---");
+
+// 1. Changing a root-level primitive property in the shallow copy
+shallowCopy.somePrimitive = 10; 
+console.log("shallowCopy.somePrimitive changed to:", shallowCopy.somePrimitive); 
+console.log("Original Object's somePrimitive:", originalObject.somePrimitive); // Original unaffected
+
+// 2. Changing a root-level primitive property that was added to illustrate the point
+shallowCopy.anotherPrimitive = "world";
+console.log("shallowCopy.anotherPrimitive changed to:", shallowCopy.anotherPrimitive);
+console.log("Original Object's anotherPrimitive:", originalObject.anotherPrimitive); // Original unaffected
+
+
+// 3. Modifying a property *within* a nested object in the shallow copy
+shallowCopy.someReference.someNestedPrim = 15;
+console.log("shallowCopy.someReference.someNestedPrim changed to:", shallowCopy.someReference.someNestedPrim); 
+console.log("Original Object's someReference.someNestedPrim:", originalObject.someReference.someNestedPrim); // Original AFFECTED
+
+
+// 4. Modifying a nested array in the shallow copy
+shallowCopy.someReference.someNestedRef.push("c"); 
+console.log("shallowCopy.someReference.someNestedRef after push:", JSON.stringify(shallowCopy.someReference.someNestedRef)); 
+console.log("Original Object's someReference.someNestedRef after push:", JSON.stringify(originalObject.someReference.someNestedRef)); // Original AFFECTED
+
+// 5. Reassigning a root-level reference property in the shallow copy
+shallowCopy.someReference = { newProperty: true };
+console.log("shallowCopy.someReference reassigned to:", JSON.stringify(shallowCopy.someReference));
+console.log("Original Object's someReference:", JSON.stringify(originalObject.someReference)); // Original still points to the old object

shallowVSDeepCopy.test.js

@@ -0,0 +1,85 @@
+// import {describe, it} from 'node:test';
+import assert from 'node:assert/strict';
+import {jest} from '@jest/globals';
+import util from 'node:util';
+import {style} from './styles.js';
+util.inspect.defaultOptions.depth = null; // show full objects
+// util.inspect.defaultOptions.depth = 0; // show truncated objects
+// util.inspect.defaultOptions.compact = true; // dont break objects to new lines
+// util.inspect.defaultOptions.compact = false; // break objects to new lines
+
+// suppress jests tracing console logs
+import console from 'console';
+const jestConsole = console;
+
+beforeEach(() => {
+    global.console = console;
+    console.log(style.color(255,0,255),'▷',style.reset,style.color(39),expect.getState().currentTestName,style.reset,'\n'); });
+
+afterEach(() => {
+    global.console = jestConsole;
+    console.log(style.color(99), style.hr.double, style.reset);
+});
+
+describe('shallowVSDeepCopy', () => {
+  it('Shallow-Copy VS Deep-Copy concept in JS', () => {
+
+    const originalObject = {
+      somePrimitive: 3,
+      someReference: {
+        someNestedPrim: 7,
+        someNestedRef: ["a", "b"]
+      },
+      anotherPrimitive: "hello" 
+    };
+
+    // Create a shallow copy using the spread syntax
+    const shallowCopy = { ...originalObject };
+
+    console.log(style.bold,style.underline,style.blue,"--- Initial State ---",style.reset);
+    console.log("Original Object:", originalObject);
+    console.log("Shallow Copy:", shallowCopy, "\n");
+
+    console.log(style.bold,style.underline,style.blue,"--- Modifying the shallow copy ---",style.reset);
+
+    // 1. Changing a root-level primitive property in the shallow copy
+    console.log(style.red,"1. Changing a root-level primitive property in the shallow copy", style.reset);
+    
+    shallowCopy.somePrimitive = 10; 
+    console.log("shallowCopy.somePrimitive changed to:", shallowCopy.somePrimitive); 
+    console.log("Original Object's somePrimitive:", originalObject.somePrimitive, style.italic, style.magenta, "// Original unaffected\n", style.reset); // Original unaffected
+
+    // 2. Changing a root-level primitive property that was added to illustrate the point
+    console.log(style.red,"2. Changing a root-level primitive property that was added to illustrate the point", style.reset);
+
+    shallowCopy.anotherPrimitive = "world";
+    console.log("shallowCopy.anotherPrimitive changed to:", shallowCopy.anotherPrimitive);
+    console.log("Original Object's anotherPrimitive:", originalObject.anotherPrimitive, style.italic, style.magenta, "// Original unaffected\n", style.reset); // Original unaffected
+
+
+    // 3. Modifying a property *within* a nested object in the shallow copy
+    console.log(style.red,"3. Modifying a property *within* a nested object in the shallow copy", style.reset);
+
+    shallowCopy.someReference.someNestedPrim = 15;
+    console.log("shallowCopy.someReference.someNestedPrim changed to:", shallowCopy.someReference.someNestedPrim); 
+    console.log("Original Object's someReference.someNestedPrim:", originalObject.someReference.someNestedPrim, style.italic, style.magenta, "// Original AFFECTED\n", style.reset); // Original AFFECTED
+
+
+    // 4. Modifying a nested array in the shallow copy
+    console.log(style.red,"4. Modifying a nested array in the shallow copy", style.reset);
+
+    shallowCopy.someReference.someNestedRef.push("c"); 
+    console.log("shallowCopy.someReference.someNestedRef after push:", shallowCopy.someReference.someNestedRef); 
+    console.log("Original Object's someReference.someNestedRef after push:", originalObject.someReference.someNestedRef, style.italic, style.magenta, "// Original AFFECTED\n", style.reset); // Original AFFECTED
+
+    // 5. Reassigning a root-level reference property in the shallow copy
+    console.log(style.red,"5. Reassigning a root-level reference property in the shallow copy", style.reset);
+
+    shallowCopy.someReference = { newProperty: true };
+    console.log("shallowCopy.someReference reassigned to:", shallowCopy.someReference);
+    console.log("Original Object's someReference:", originalObject.someReference, style.italic, style.magenta, "// Original still points to the old object", style.reset); // Original still points to the old object
+  });
+
+});
+
+