Diving into JavaScript: Printing, Commenting, Data Types, and Expressions

Overview

Greetings! Today, we're about to start an exciting journey into the world of JavaScript . We'll focus on JavaScript fundamentals - printing, comments, data types, and expressions. Imagine you can make a website play a game with its visitors or react to their actions like a fellow human. That's what JavaScript does! Ready to dive in? Let's start.

Dive into JavaScript

JavaScript brings static web pages to life by making them interactive! Every language has syntax — rules about how sentences (or in our case, statements) should be written. JavaScript is no exception. Let's have a quick look: JavaScript // Outputting text to the console console.log("Hello, World!"); In the above example, we're giving a shoutout to the world: "Hello, World!" . You'll often see semicolons (;) at the end of statements in JavaScript. In JavaScript this is optional as it has a feature called Automatic Semicolon Insertion (ASI) that can add them for you. Many developers include them explicitly for clarity and consistency. A great start, isn't it? Let's keep going.

Commenting in JavaScript

Coding isn’t just for computers. You also leave notes for fellow humans — future developers or even your future self — known as 'comments'. A comment can either be a one-liner that uses //, or a note stretching across multiple lines within /* and */ . These comments explain your code’s purpose, design, and functioning, making reading code much easier. JavaScript // Single line comment /* Multi-line comment console.log(600); The above line won't output anything, since it's within a comment */ An essential thing to note is that, unlike JavaScript statements, comments do not need to end with a semi-colon (;). This is because they're not executable code and are ignored by the JavaScript engine.

Understanding Data Types in JavaScript

JavaScript works with many data types, but let's start with three fundamental ones: Numbers, Strings, and Booleans. Try entering the following commands and observe the results: JavaScript console.log(42); // prints 42 console.log("Learning is fun!"); // prints "Learning is fun!" console.log(true); // prints true

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Let's move on to expressions, which are pieces of code that produce a value. It can be numbers, strings, or boolean values. For instance, 2 + 2 yields 4, and "Hello, " + "World!" results in "Hello, World!". Experiment with basic arithmetic operations, like addition (+), subtraction (-), multiplication (*), division (/), and modulo (%, the remainder from division) in the CodeSignal IDE.

Take a look at this combination of comments, print commands, and expressions:

JavaScript

console.log(2 + 2); // Outputs: 4
console.log("2 + 2"); // Outputs: 2 + 2
console.log("Hello, " + "World!"); // Outputs: Hello, World!
console.log("2" + "2"); // Outputs: 22, because + operation applied on strings concatenates them
console.log(2 + 2 > 5); // Outputs: false, because 2 + 2 is not greater than 5.

console.log(2 + 2); // Outputs: 4
console.log("2 + 2"); // Outputs: 2 + 2
console.log("Hello, " + "World!"); // Outputs: Hello, World!
console.log("2" + "2"); // Outputs: 22, because + operation applied on strings concatenates them
console.log(2 + 2 > 5); // Outputs: false, because 2 + 2 is not greater than 5.

Comparison operators include < (less than), > (greater than), <= (less than or equal to), >= (greater than or equal to). They are used to compare two values and return boolean true or false.

JavaScript

console.log(5 < 6);   // true
console.log(5 > 6);   // false
console.log(5 <= 5);  // true
console.log(5 >= 10); // false

console.log(5 < 6);   // true
console.log(5 > 6);   // false
console.log(5 <= 5);  // true
console.log(5 >= 10); // false

Fantastic! You've taken some confident strides into the JavaScript world. We've touched upon JavaScript printing, comments, data types, and expressions. Now, you're all set to roll up your sleeves and put your newfound knowledge to practice! So, let's move onto the practice tasks and flex those JavaScript muscles!

Overview

Dive into JavaScript

Commenting in JavaScript

Understanding Data Types in JavaScript

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Making JavaScript Expressive

Comparison Operators

Lesson Summary