Create an Object Literal

let and const

JavaScript used to have only one keyword for creating a variable: var. For example, to create a variable named temperature with a value of 98.9 you could do this: var temperature = 98.9.

Two new keywords were introduced in ES2015 (a newer version of JavaScript): let and const. Most JavaScript programmers now use those two keywords. However, var works and you'll still see it around a lot. To get familiar with these keywords follow these rules:

const

Use const (which is short for constant) to store a value that won't change. For example, if you're setting the sales tax rate -- which won't change while your program is running you'd use const. For example: const taxRate = 7.5;

let

Use let to store a value that changes while the program runs. For example, if you're keeping track of a changing score, or the number of times a person clicks on a web page, use let: let totalSales = 0;

As with var you can store any type of data in a variable defined with let or const -- numbers, strings, arrays, objects, Boolean values, etc. If you are confused about whether to use let or const the rule of thumb is if you're in doubt, use const.

To learn more, check out the workshop Defining Variables with let and const

Code for completed solution

let book = {
  title: "Harry Potter and the Sorcerer's Stone",
  author: "J.K. Rowling",
  publish_year: 1997
};
for (book_property in book) {
 console.log(book_property + ": " + book[book_property]);
}