JavaScript
📦 Variables and data types
Store information with let and const, and learn the fundamental data types.
What you'll learn
- Declare variables with
letandconstand decide which one to use depending on whether the value is reassigned. - Distinguish the primitive types (
number,string,boolean,null,undefined) and inspect them withtypeof. - Tell
undefinedapart fromnulland explain the temporal dead zone (TDZ) oflet/const.
Lessons
Declaring variables: let and constHow to store and reuse values. Primitive data typesnumber, string, boolean, null, undefined.Practice this module in the app
DevPath is a hands-on course: you read the theory here; in the app you put it into practice with exercises that really run, offline.
Start free in the app →