Master JavaScript from basics to advanced
A while loop repeats code as long as a condition stays true. Learn the syntax, see practical examples, and understand when a while loop is the right choice over a for loop.
The for loop is the most common way to repeat code in JavaScript. Learn the three-part syntax, how each part works, and how to write clean, readable for loops.
Learn every use of the spread operator (...) with arrays: copying, merging, inserting elements, converting iterables, and passing array elements as function arguments.
The spread operator creates shallow copies. Learn what that means for nested objects and arrays, how to avoid shared reference bugs, and when to use structuredClone.
map() returns a new array. forEach() returns undefined. Learn the key differences, when to use each, and why choosing the right one makes your code cleaner.
some() checks if any element passes a test. every() checks if all elements pass. Learn how these boolean array methods work with clear examples and practical use cases.
flatMap() combines map() and flat(1) into a single method. Learn how to map and flatten in one pass with clear examples and practical use cases.
filter() creates a new array with only the elements that pass a test. Learn how to select, exclude, and refine array data with clear examples.
reduce() turns an array into a single value by running an accumulator function on every element. Learn summing, grouping, flattening, and more.
Destructuring unpacks array values into variables in one line. Learn the syntax, default values, skipping elements, rest patterns, and practical use cases.
Learn four ways to remove duplicate values from JavaScript arrays: Set, filter, reduce, and forEach. Compare approaches for primitives and objects.
Learn the JavaScript Set object for storing unique values of any type. Covers add, delete, has, iteration, removing duplicates, and set operations.
