Mastering JavaScript Arrays: Essential Functions and Methods

Tutorial: Array Functions - every()

Hey there, coder! Today we're going to explore another powerful array function in JavaScript: every(). This function is used to check if all elements in an array satisfy a certain condition. Let's dive in!

The Problem: Check if any product in an inventory is out of stock

Imagine you're a store manager, and you need to check if any product in your inventory is out of stock. You have an array of objects, where each object represents a product with its name, quantity, and stock status. Your task is to write a function that checks if any product is out of stock.

Create a sample inventory array

In your index.js file, create a sample inventory array:

const inventory = [
	{ name: "Apple Watch", quantity: 10, stock: true },
	{ name: "Samsung TV", quantity: 5, stock: false },
	{ name: "Nike Shoes", quantity: 20, stock: true },
	{ name: "PlayStation", quantity: 0, stock: false },
]

Write a function to check if any product is out of stock

Create a function isOutOfStock() that takes the inventory array as an argument. This function should return true if any product is out of stock, and false otherwise.

function isOutOfStock(inventory) {
	// Your code here
}

Use the every() function

To solve this problem, we can use the every() function, which returns true if every element in the array satisfies the provided test function. In our case, we want to check if every product is in stock. If any product is out of stock, the function should return false.

Add the following code to your isOutOfStock() function:

function isOutOfStock(inventory) {
	return inventory.every((product) => product.stock)
}

Here, we're using an arrow function as the test function for every(). The arrow function takes a product object as an argument and checks if its stock property is true. If any product has stock set to false, the every() function will return false.

Run the code and check the output

Click the "Run" button to execute your code. You should see the output in the console.

Expected Output:

false

This is because the Samsung TV and PlayStation products are out of stock.

Exercise: Modify the function to return an array of out-of-stock products

Modify the isOutOfStock() function to return an array of products that are out of stock. Use the filter() function to achieve this.

Hint: You can use the filter() function to create a new array of products that have stock set to false.

When you're ready, click the "Run" button to see the output.

That's it! You've learned how to use the every() function to check if every element in an array satisfies a condition. Well done!

Remember, practice makes perfect. Try experimenting with different array functions and scenarios to solidify your understanding. Happy coding!