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Walk through the solution to the second project in this practice session and see how to modify properties on a simple object literal.
Code for completed solution
let product = {
name: "Chair",
inventory: 10,
unit_price: 45.99
};
function addInventory(prod, quantity) {
prod.inventory += quantity;
console.log(quantity + " " + prod.name + "s added to the inventory.");
console.log(prod.inventory + " " + prod.name + "s in stock.");
}
addInventory(product, 3);
function processSale(prod, quantity) {
prod.inventory -= quantity;
console.log(quantity + " " + prod.name + "s sold");
return quantity * prod.unit_price;
}
console.log("Total sale: $" + processSale(product, 3));
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0:00
For this project, you had to create an object literal and
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a couple of functions that manipulate the values in the object.
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Let's start by creating the object in the 2_product.js file.
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I'll call this object product and add three properties with three values.
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Chair, we have 20 of them in stock, and their unit price is $45.99.
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Now here I'm using the newer syntax with the let keyword to create the variable.
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You could use var just as well and it still works.
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But check the teacher's notes if you wanna understand the difference between var and
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let, and why we now use let.
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Now, this is just a basic object literal with three properties and three values.
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Next, I'll create a function that manipulates the value of the inventory
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property of the product object.
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I'll call the function addInventory, and it accepts two arguments,
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the object itself, and the number of items to add to the inventory.
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So to adjust the inventory just add the quantity to the inventory property.
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Remember you can use dot syntax to access a property on an object.
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You can then assign a new value to that property.
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In this case I'll use the += operator, And
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add the quantity that's passed into the function.
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In other words, if we add five new chairs,
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we'll add five to the inventory property of this object.
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Now we'll log out a message to the console.
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We'll print the quantity, and which product we add to that quantity too.
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I'll save this and call the function down here.
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I'll pass in our product, and let's say we add three to the inventory.
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I'll save the file, and in the console down here I'll type,
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node 2_product.js to run our code.
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3 Chairs added to the inventory.
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If you're following along, and your script isn't working, just pause this video and
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compare your code to the code posted in the teacher's notes.
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Finally, I'll log out the current inventory after we've changed,
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that is after we've added items to the inventory.
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So, we'll log out prod.inventory, which gives you the new number of items in
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the inventory, as well as the products name, and
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a little bit of message saying that we have those in stock.
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Again, I'll save this file, go to the console, And run the code.
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3 Chairs added to the inventory.
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23 Chairs in stock.
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There are many ways you can improve this function.
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For example, you might want to make sure that the quantity that's passed into
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the function is a positive whole number.
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We can't add half an item, nor can we add a string to the inventory.
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The next function returns a sales amount and deducts products from the inventory.
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The function's called processSale and
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takes the product object in a quantity as arguments.
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In this case,
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because we're selling an item, we'll be removing it from our inventory.
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So, we'll use the -= operator.
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I'll access the inventory amount and
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subtract from it the quantity that's passed in.
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Let's log out the quantity sold.
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To test this, we'll call this function.
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Pass in our product, object, and let's say we'll sell five chairs.
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Let's test this in the console.
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I'll clear the console and call the program again.
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3 Chairs added to the inventory.
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23 Chairs in stock.
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5 Chairs sold.
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All right, looks good.
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Finally, let's return the sales total.
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I'll go back to the processSale() function and add a return statement.
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Now we're returning the total sales price, which is a quantity,
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how many chairs were purchased times the price per chair,
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that's the unit price, and then let's log out the results of this,
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To the console By calling the function,
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passing in the product, and let’s say we’ll buy three chairs this time.
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Let's see what happens.
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Great!
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3 Chairs sold.
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The total sale $137.97.
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If you had trouble with this practice session don't worry,
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compare your code to the code the sit in the teachers notes below.
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Look very carefully at what tripped you up, study it, and
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figure out how to fix your code.
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Failure is the best way to learn and
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we don't usually get things right on the first try.
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Now are you ready for the final practice challenge?
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I'll see you in the next video.
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