Key Concepts

Review core concepts you need to learn to master this subject

JavaScript

console.log()

Strings

Numbers

Booleans

Null

Arithmetic Operators

String .length

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JavaScript

JavaScript is a programming language that powers the dynamic behavior on most websites. Alongside HTML and CSS, it is a core technology that makes the web run.

Introduction to JavaScript
Lesson 1 of 2
  1. 1
    What is JavaScript?
    Last year, millions of learners from our community started with JavaScript. Why? JavaScript is primarily known as the language of most modern web browsers, and its early quirks gave it a bit of a b…
    Start
  2. 2
    Console
    The console is a panel that displays important messages, like errors, for developers. Much of the work the computer does with our code is invisible to us by default. If we want to see things appear…
    Start
  3. 3
    Comments
    Programming is often highly collaborative. In addition, our own code can quickly become difficult to understand when we return to it— sometimes only an hour later! For these reasons, it’s oft…
    Start
  4. 4
    Data Types
    Data types are the classifications we give to the different kinds of data that we use in programming. In JavaScript, there are seven fundamental data types: - Number: Any number, including nu…
    Start
  5. 5
    Arithmetic Operators
    Basic arithmetic often comes in handy when programming. An operator is a character that performs a task in our code. JavaScript has several built-in arithmetic operators, that allow us to per…
    Start
  6. 6
    String Concatenation
    Operators aren’t just for numbers! When a + operator is used on two strings, it appends the right string to the left string: console.log(‘hi’ + ‘ya’); // Prints ‘hiya’ console.log(‘wo’ + ‘ah’); /…
    Start
  7. 7
    Properties
    When you introduce a new piece of data into a JavaScript program, the browser saves it as an instance of the data type. Every string instance has a property called length that stores the number of…
    Start
  8. 8
    Methods
    Remember that methods are actions we can perform. JavaScript provides a number of string methods. We call, or use, these methods by appending an instance with: - a period (the dot operator) - t…
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  9. 9
    Built-in Objects
    In addition to console, there are other objects built into JavaScript . Down the line, you’ll build your own objects, but for now these “built-in” objects are full of useful functionality. For e…
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  10. 10
    Review
    Let’s take one more glance at the concepts we just learned: - Data is printed, or logged, to the console, a panel that displays messages, with console.log(). - We can write single-line comments wi…
    Start

What you'll create

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How you'll master it

Stress-test your knowledge with quizzes that help commit syntax to memory

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