Key Concepts

Review core concepts you need to learn to master this subject

JavaScript

Methods

Libraries

console.log()

Numbers

String .length

Data Instances

Booleans

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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.

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Introduction to JavaScript
Lesson 1 of 2
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  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 in arithmetic operators, that allow us to …
    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’); /…
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  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…
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  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…
    Start
  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
  1. 1
    Variables
    In programming, a variable is a container for a value. You can think of variables as little containers for information that live in a computer’s memory. Information stored in variables, such as a…
    Start
  2. 2
    Create a Variable: var
    There were a lot of changes introduced in the ES6 version of JavaScript in 2015. One of the biggest changes was two new keywords, let and const, to create, or declare, variables. Prior to the ES6…
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  3. 3
    Create a Variable: let
    As mentioned in the previous exercise, the let keyword was introduced in ES6. The let keyword signals that the variable can be reassigned a different value. Take a look at the example: let meal = …
    Start
  4. 4
    Create a Variable: const
    The const keyword was also introduced in ES6, and is short for the word constant. Just like with var and let you can store any value in a const variable. The way you declare a const variable and as…
    Start
  5. 5
    Mathematical Assignment Operators
    Let’s consider how we can use variables and math operators to calculate new values and assign them to a variable. Check out the example below: let w = 4; w = w + 1; console.log(w); // Output: 5 …
    Start
  6. 6
    The Increment and Decrement Operator
    Other mathematical assignment operators include the increment operator (++) and decrement operator (–). The increment operator will increase the value of the variable by 1. The decrement ope…
    Start
  7. 7
    String Concatenation with Variables
    In previous exercises, we assigned strings to variables. Now, let’s go over how to connect, or concatenate, strings in variables. The + operator can be used to combine two string values even if th…
    Start
  8. 8
    String Interpolation
    In the ES6 version of JavaScript, we can insert, or interpolate, variables into strings using template literals. Check out the following example where a template literal is used to log strings …
    Start
  9. 9
    typeof operator
    While writing code, it can be useful to keep track of the data types of the variables in your program. If you need to check the data type of a variable’s value, you can use the typeof operator. T…
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  10. 10
    Review Variables
    Nice work! This lesson introduced you to variables, a powerful concept you will use in all your future programming endeavors. Let’s review what we learned: * Variables hold reusable data in a pro…
    Start

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