Connect Four

Build a scrollable list that automatically loads more items as the user reaches the bottom.

Infinite Scroll

Build a nested checkbox tree where checking a parent checks its children and a partly checked parent shows an indeterminate state.

Nested Checkboxes

A transfer list is a UI component for moving items between two lists, often used to manage and organize multiple selections.

Transfer List

React component for efficiently rendering large lists and tabular data.

Virtualized List

polyfill function that replicates the behavior of the built-in Function.prototype.apply() method.

Polyfill: apply()

polyfill function that replicates the behavior of the built-in Function.prototype.bind() method.

Polyfill: bind( )

polyfill function that replicates the behavior of the built-in Function.prototype.call() method.

Polyfill: call( )

A simple javascript utility for conditionally joining classNames together.

classnames

A function that clears all active JavaScript intervals at once.

clearAllIntervals

A function that clears all active JavaScript timeouts at once.

clearAllTimeouts

Implement a simple assertion function similar to Jest's expect function

Custom Assertion Function

Implement a myExtends helper that mimics ES5 prototype-based inheritance by combining two constructor functions into one, with constructor stealing, a shared prototype chain, and static inheritance.

ES5 Extends

Takes a nested array and merges all its layers into a single, flat array.

Flatten Array

Build your own version of JSON.stringify that serializes JavaScript values to JSON strings.

Implement JSON.stringify()

Safely access deeply nested object properties using a path string or array.

Implement lodash.get()

Implement a Least Recently Used cache with O(1) get and put operations.

LRU Cache

Min Height of DOM Tree

Build your own Promise.reject — return a promise that is immediately rejected with a given reason.

promise.reject()

Build the ES2024 Promise.withResolvers — return a promise along with its resolve and reject functions as a plain object.

Promise.withResolvers()

Recreate setInterval behavior using only setTimeout.

Implement setInterval using setTimeout

Highlight search matches in a DOM tree even when the match spans across multiple elements and text nodes.

Text Search II

Highlight all occurrences of a query string inside a DOM tree by wrapping matches in bold tags.

Text Search

The TimerManager class in JavaScript manages multiple timers, offering multiple functionalities.

Timer Manager

Traverse DOM tree and flatten it into a one-dimensional array in breadth-first order.

Traverse DOM Tree

Build a tree from slash-delimited paths, replay a sequence of clicks that cascade selection down to descendants and recompute every ancestor, then render the tree with selected, not selected, and partial states.

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