JavaScript Foundations

About this course

A first programming course where you write code from the third lesson onward. Every exercise runs in your browser and checks your work against tests, so a failure tells you what was expected and what your code actually produced rather than just marking it wrong. It covers what almost every program does: hold values, change them, decide, and repeat. Variables and the three ways to declare one, the type coercion that causes most beginner confusion, conditionals and the falsy values that quietly break things, loops and the off-by-one at the heart of them, and functions that do one job. The last section is about debugging, which is most of programming and is almost never taught. It finishes with a deliberately broken function carrying three bugs you have already met, to be fixed by reading the failures rather than guessing. JavaScript is the language because it runs where you already are, but variables, conditionals, loops and functions look nearly the same in Python, Java, C# or Go.

What you will learn

• Declare variables correctly and explain why const is the sensible default
• Predict how JavaScript converts between types, and avoid the bugs that causes
• Write conditionals that handle boundaries and falsy values correctly
• Use loops and the accumulator pattern to process collections
• Break a problem into small functions that each do one job
• Read an error message and locate a bug by narrowing rather than guessing

Before you begin

• No programming experience needed
• A browser. Nothing to install
• Willingness to get things wrong repeatedly, which is the activity rather than a setback