Sending hero2 to the console, we can see we have created a new Mage based off the constructor. We want to make this open-source project available for people all around the world. We can pass button.click around anywhere, and the value of this will always be correct. The Clock class is written in functional style. In practice, we often need to create many objects of the same kind, like users, or goods or whatever. The only difference in the syntax of the initialization is using the class keyword instead of function, and assigning the properties inside a constructor() method. You can read more about prototypes in our Understanding Prototypes and Inheritance in JavaScript tutorial. Just like functions, classes can be defined inside another expression, passed around, returned, assigned, etc. Using private fields, the definition can be refined as below. How To Use the JavaScript Developer Console, How To Write Your First JavaScript Program, Understanding Syntax and Code Structure in JavaScript, How To Index, Split, and Manipulate Strings in JavaScript, Understanding Variables, Scope, and Hoisting in JavaScript, How To Do Math in JavaScript with Operators, How To Use Array Methods in JavaScript: Mutator Methods, How To Use Array Methods in JavaScript: Accessor Methods, How To Use Array Methods in JavaScript: Iteration Methods, Understanding Date and Time in JavaScript, How To Write Conditional Statements in JavaScript, How To Use the Switch Statement in JavaScript, Using While Loops and Do...While Loops in JavaScript, For Loops, For...Of Loops and For...In Loops in JavaScript, Understanding Prototypes and Inheritance in JavaScript, Understanding This, Bind, Call, and Apply in JavaScript, Understanding Map and Set Objects in JavaScript, Understanding Default Parameters in JavaScript, Understanding Destructuring, Rest Parameters, and Spread Syntax in JavaScript, Understanding Template Literals in JavaScript, Understanding Arrow Functions in JavaScript, Understanding the Event Loop, Callbacks, Promises, and Async/Await in JavaScript, Next in series: How To Use Object Methods in JavaScript, Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Class basic syntax. Attempting to do so produces a SyntaxError. For more information, see private class fields. Classes are in fact \"special functions\", and just as you can define function expressions and function declarations, the class syntax has two components: class expressions and class declarations. In the next chapters we’ll learn more about classes, including inheritance and other features. A constructor can use the super keyword to call the constructor of the super class. For example, unlike a regular function, it must be called with new: Also, a string representation of a class constructor in most JavaScript engines starts with the “class…”. We will use extends to refer to the parent class. The clock ticks in the console, open it to see. We will print hero2 to the console and view the output. Here’s an example with a computed method name using brackets [...]: Such features are easy to remember, as they resemble that of literal objects. This behavior will be the same even if the "use strict" directive isn't present, because code within the class body's syntactic boundary is always executed in strict mode. One may also extend traditional function-based "classes": Note that classes cannot extend regular (non-constructible) objects. JavaScript is the world's most popular programming language. Supporting each other to make an impact. JavaScript is a high-level, object-based, dynamic scripting language popular as a tool for making webpages interactive.