JavaScript

Update text, attributes, classes and styles safely, and why textContent beats innerHTML for user data.

Listen for clicks, input and keyboard events, the event object, and preventDefault.

What JavaScript does in the browser and on servers, how it relates to HTML and CSS, and what ECMAScript means.

Read form values, handle submit, give live validation feedback and send data without a page reload.

Run code in the browser console, load scripts with the script element and defer, and run files with Node.js.

Declare variables with let and const, why var is avoided, and naming conventions.

Primitive types, objects, null versus undefined, and checking types with typeof.

Arithmetic, assignment, logical and comparison operators, type coercion and why strict equality is the default.

Create and combine strings, template literals, and everyday string methods.

Number behaviour, floating-point surprises, parsing numbers, rounding and the Math object.

Make decisions with if and else, truthy and falsy values, switch and the ternary operator.

Repeat work with each loop type, break and continue, and which loop suits arrays and objects.

Define and call functions, default parameters, return values and function expressions.

Arrow function syntax, implicit returns, and how arrows differ from regular functions.