May 14, 2025
diff --git a/README.md b/README.md
 const req = newRequestModule;
 inventoryTracker("apples", req, "www.inventory-awesome.io");
 ```
 **[⬆ back to top](#table-of-contents)**

 #### Pure Functions vs. Side Effects

 - A **pure function** only uses its input values and doesn’t change anything outside itself.
 - A **side effect** is any change to external state (mutating arguments, globals, etc.).

 **Why?**
 - Predictable: gives the same result every time for the same inputs.
 - Easy to test: no hidden state to reset or mock.
 - Safe to reuse and refactor without unintended consequences.

 **Bad:**
 ```js
 let total = 0;

 function addToCart(cart, item) {
  cart.push(item);       // ← side effect: changing external cart
  total += item.price;   // ← side effect: changes external `total`
  return cart.length;
 }
 ```
 **Good:**
 ```js
 function addToCart(cart, item) {
  // returns a new cart array without touching the original
  return [...cart, item];
 }

 function calculateTotal(cart) {
  // pure computation: only reads input, never writes out
  return cart.reduce((sum, item) => sum + item.price, 0);
 }
 ```

 **[⬆ back to top](#table-of-contents)**

 delete employee.name;
 console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
 ```
 **[⬆ back to top](#table-of-contents)**

 #### Destructuring Defaults & Nested Destructuring

 It lets you set default values for object properties right in the function signature and prevents errors if a nested object isn’t provided.

 **Why?**
 - Eliminates repetitive `||` defaulting.
 - You can see what values the function uses and their fallback values right in its definition.
 - Prevents runtime errors when nested objects are omitted.

 **Bad:**
 ```js
 function connectToDatabase(opts) {
  const host = opts.host || 'localhost';
  const port = opts.port || 80;
  const db   = opts.db   || { name: 'test' };
 }
 ```

 **Good:**
 ```js
 function connectToDatabase({
  host = 'localhost',
  port = 80,
  db: { name = 'test' } = {}
 } = {}) {
 }
 ```

 **[⬆ back to top](#table-of-contents)**
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1033,6 +1033,40 @@ function newRequestModule(url) {
		const req = newRequestModule;
		inventoryTracker("apples", req, "www.inventory-awesome.io");
		```
		[⬆ back to top](#table-of-contents)

		#### Pure Functions vs. Side Effects

		- A pure function only uses its input values and doesn’t change anything outside itself.
		- A side effect is any change to external state (mutating arguments, globals, etc.).

		Why?
		- Predictable: gives the same result every time for the same inputs.
		- Easy to test: no hidden state to reset or mock.
		- Safe to reuse and refactor without unintended consequences.

		Bad:
		```js
		let total = 0;

		function addToCart(cart, item) {
		cart.push(item); // ← side effect: changing external cart
		total += item.price; // ← side effect: changes external `total`
		return cart.length;
		}
		```
		Good:
		```js
		function addToCart(cart, item) {
		// returns a new cart array without touching the original
		return [...cart, item];
		}

		function calculateTotal(cart) {
		// pure computation: only reads input, never writes out
		return cart.reduce((sum, item) => sum + item.price, 0);
		}
		```

		[⬆ back to top](#table-of-contents)

Expand DownExpand Up		@@ -1136,6 +1170,35 @@ console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
		delete employee.name;
		console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
		```
		[⬆ back to top](#table-of-contents)

		#### Destructuring Defaults & Nested Destructuring

		It lets you set default values for object properties right in the function signature and prevents errors if a nested object isn’t provided.

		Why?
		- Eliminates repetitive `\|\|` defaulting.
		- You can see what values the function uses and their fallback values right in its definition.
		- Prevents runtime errors when nested objects are omitted.

		Bad:
		```js
		function connectToDatabase(opts) {
		const host = opts.host \|\| 'localhost';
		const port = opts.port \|\| 80;
		const db = opts.db \|\| { name: 'test' };
		}
		```

		Good:
		```js
		function connectToDatabase({
		host = 'localhost',
		port = 80,
		db: { name = 'test' } = {}
		} = {}) {
		}
		```

		[⬆ back to top](#table-of-contents)

Expand Down