Useful ES6 features

ES6 was released in 2015, and it introduced a lot of new features. ECMAScript is a standardized scripting language, and JavaScript is one implementation of it. In this section, we will go through the most important features released in ES6 that we will be using in the following sections.

Constants and variables

Constants, or immutable variables, can be defined by using a const keyword, as shown in the following code snippet. When using the const keyword, the variable content cannot be reassigned:

const PI = 3.14159;

Now, you will get an error if you try to reassign the PI value, as indicated in the following screenshot:

Figure 8.4: Assignment to constant variable

The const is block-scoped. This means that the const variable can only be used inside the block in which it is defined. In practice, the block is the area between curly brackets {}. If const is defined outside of any function or block, it becomes a global variable, and you...