Numbers

[00:00] Alright. Like I said, hopefully, it was pretty straightforward. We're gonna console log each one of these. The AI is really good at this. Let's talk about what it's doing in each case.

[00:08] So, it's actually kinda similar to concatenation, with this plus character, but it's doing a completely different thing. Rather than taking two strings and putting them together, we're actually taking these two numbers and, summing them together. And so here, if I save this twenty five and seventeen, evidently, it's 42. We could actually put one of these in a string and you can add those together and now it turns the whole thing into a string. This is what we call coercion.

[00:35] We are coercing this 17 into a string so that it can be properly added to another string. So if one of these things is a string, you can't add a string to a number. So we're going to turn the other one from a number into a string and then we can add them together. This might catch you, off guard in in some ways. Sometimes, you're going to have a variable that contains a string that looks like a number.

[00:57] So like it contains the number 25, but it's actually a string data type. And so that's gonna throw you, for a loop sometimes. If you ever see something like this, that's what's going on and you need to convert that string into a number and you'll learn how to do that a little bit later. So, here we're adding those numbers together. Here we're multiplying.

[01:15] Here we're dividing. And then parenthesis works the same way as the order of operations in your regular math class that you've, taken before. So, we've got 10 plus five times two, fifteen times 30 or times two is 30. So there you go. That is, number expressions.

[01:33] There are actually a bunch of others. So you've got, exponential or exponents. Yeah. And you've got, in fact, there's a whole library of math operations, sine, cosine, everything, not through operators like this, but, using a math object that's globally available. And you can look at that later.

[01:52] But this is the syntax for operating with numbers. I hope you enjoyed it.

[00:00] Alright. Let's talk about numbers. So we've got those strings. Now we have number expressions. So that, it pretty much works the way that you would expect.

[00:12] You just need to know which characters, like, what's divide, what's multiply, what's plus. But it's it's all pretty much what you expect. So I'm not really gonna do too much to introduce you to this concept. Go ahead and follow the instructions, and we'll see you on the other side.

Learning to program can feel overwhelming. There are countless tutorials, boot camps, and YouTube videos all pulling you in different directions, and most of them assume you already know something.

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## Expressions & Output

Every program needs a way to tell you what it's doing. Without output, you're flying blind-- writing code with no way to verify it works. This is the very first skill you need as a developer.

In this section, you'll get your programs talking back to you while learning the building blocks of every piece of code you'll ever write:

- Outputting values with `console.log`
- String expressions and concatenation
- Number expressions and arithmetic operators
- Escaping special characters in strings
- Template literals with interpolation and multiline support

## Variables

Hardcoded values can only get you so far. Real programs need to store, reference, and update data as they run. Without a solid understanding of how variables work, you'll constantly be confused by unexpected behavior.

Variables are foundational to every program you'll ever write. Here you'll learn how to declare them, when to use each type, and a critical nuance that trips up even experienced developers:

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- Naming conventions and casing (camelCase, SCREAMING_SNAKE_CASE)
- Reassigning values with `let` and compound operators like `+=`
- The important distinction between reassignment and mutation
- Why `const` doesn't always mean the value can't change

## Primitive Types

JavaScript has types whether you think about them or not. Every value in every variable carries a type, and ignoring that fact leads to bugs that are hard to track down. TypeScript makes these types explicit, catching entire categories of errors before your code ever runs.

This section introduces you to all seven primitive types and how TypeScript helps you work with them safely:

- Explicit type annotations with `number`, `string`, and `boolean`
- The difference between `null` and `undefined`
- Special types: `bigint` for arbitrarily large numbers and `symbol` for unique identifiers
- Type coercion and why it can surprise you
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## Comparisons & Boolean Logic

Making decisions is at the heart of every program. Should this button be enabled? Does this user have access? Is the cart empty? All of these questions boil down to comparisons and boolean logic.

Getting comparisons wrong leads to subtle bugs that are painful to debug. This section gives you the tools to write conditions that behave exactly as you'd expect:

- Loose equality (`==`) vs. strict equality (`===`) and why you should almost always use strict
- Not-equal, greater-than, and less-than-or-equal-to operators
- Combining conditions with logical AND (`&&`), OR (`||`), and NOT (`!`)
- Order of operations with logical operators
- Using parentheses to make complex conditions explicit

## Truthiness & Falsiness

JavaScript has a unique feature where every value has an inherent "truthiness" or "falsiness." This isn't a bug-- it's one of the most practical features of the language once you understand it. But misunderstanding it leads to some of the most confusing behavior new developers encounter.

Here you'll learn which values are truthy, which are falsy, and how to use this knowledge to write cleaner conditional logic:

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- Falsy values: `0`, `""`, `null`, `undefined`, `false`, and `NaN`
- Practical patterns like checking array length and optional values
- Avoiding common pitfalls with logical operators and coercion

## Functions

Up to this point, your programs run top to bottom and that's it. Functions change everything. They let you take a chunk of code, put it somewhere reusable, and call it from anywhere-- with different inputs each time.

Functions are the single most important building block for organizing and scaling your programs. This section takes you from writing your first function through passing functions as arguments to other functions:

- Function declarations with the `function` keyword
- Accepting parameters and specifying their types
- Return values and TypeScript's return type inference
- Arrow functions and implicit returns
- Passing functions as arguments to other functions
- Documenting your functions with JSDoc

## Type Inference & Arrow Functions

TypeScript is smart. You don't have to type everything explicitly-- TypeScript can often figure out the types for you by looking at your code. Knowing when to lean on inference and when to be explicit is a skill that makes your code cleaner and your development faster.

This section also covers arrow functions, a concise alternative syntax you'll see everywhere in modern JavaScript and TypeScript:

- How TypeScript infers return types from your function body
- When explicit return types help catch bugs earlier
- Converting function declarations to arrow functions
- Implicit returns for single-expression functions
- The hoisting difference between declarations and expressions
- Function expressions as first-class values

## Void & Never

Not every function returns something useful, and some code paths should never be reached. TypeScript has dedicated types for both of these situations, and understanding them helps you write more precise, self-documenting code.

This section introduces two TypeScript-specific concepts that complete your understanding of the type system's fundamentals:

- The `void` type for functions that don't return a value
- How `void` relates to `undefined` in practice
- The `never` type for functions that throw errors or never return
- Using `never` to enforce exhaustive checks
- Throwing errors to halt execution and signal failures
- Practical patterns for input validation with error throwing

Programming Foundations

Structured Data

Type Safety

Object Oriented TypeScript

Advanced TypeScript

Practical TypeScript: Foundations to Fluency

Master programming basics with our Introduction to Programming Foundations. Perfect for beginners eager to start coding and build essential skills.

Intro to Introduction To Programming Foundations

Introduction to Programming Foundations

Intro to Expressions And Output

Hello World

Escaping Strings

Strings

Template Literals

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1. Expressions And Output

Intro to Variables

Discover the key differences between let and const in JavaScript. Optimize your code with these essential ES6 variable declarations.

Let And Const

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Reassignment Vs Mutation

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2. Variables

Discover the basics of primitive types in programming. Understand integers, floats, booleans, and more to enhance your coding skills.

Intro to Primitive Types

Master numbers and strings with this guide. Enhance your coding skills by understanding data types and their applications in programming.

Numbers And Strings

Discover key differences and similarities with our in-depth comparisons. Make informed decisions with clear insights and expert analysis.

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Master Booleans and comparisons in programming. Enhance your coding skills with clear examples and practical applications. Perfect for beginners!

Booleans And Comparisons

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Bigint And Symbol

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Truthy Falsy

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3. Primitive Types

Master control flow basics in programming. Enhance your coding skills with loops, conditionals, and more. Perfect for beginners!

Intro to Control Flow

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Conditionals

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Switch Statements

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Loops

Master nested loops in programming to enhance your coding skills. Discover efficient techniques and practical examples for optimal performance.

Nested Loops

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Ternary Operator

Discover common errors, their causes, and solutions. Enhance your skills by learning to identify and fix mistakes effectively.

Errors

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4. Control Flow

Master the basics of functions in programming. Enhance your coding skills with clear examples and practical insights. Perfect for beginners!

Programming Foundations

Programming Foundations

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Numbers

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