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JavaScript Functions

Implement JavaScript functions like utility methods, polyfills, or DOM APIs.
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Lista de perguntas

Perguntas de entrevista de Front-End JavaScript — Como se prepararGuia para se preparar para perguntas de JavaScript em entrevistas para desenvolvedores front-end / web — Conceitos a saber, rubricas de entrevista e mais de 70 perguntas de prática importantes.
Guide
GUIDES
  • Make CounterImplement a function that accepts an integer value and returns a function that can be repeatedly called to return increasing values
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  • MeanImplement a function that finds the mean of the values inside an array
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  • Function.prototype.callImplement the Function.prototype.call() function that calls the function with a given `this` value and provided arguments
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  • Min ByImplement a function that finds the minimum element based on the specified criteria
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  • Type UtilitiesImplement utilities to determine primitive variable types in JavaScript
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  • useBooleanImplement a hook that manages a boolean state, with additional convenience utility methods
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  • useCounterImplement a hook that manages a counter state, with some additional convenience utility methods
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  • Array.prototype.reduceImplement the Array.prototype.reduce() method
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  • CycleImplement a function that takes one or more values and returns a function that cycles through those values each time it is called
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  • Type Utilities IIImplement utilities to determine non-primitive variable types in JavaScript
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  • useClickAnywhereImplement a hook that handles click events anywhere on the document
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  • useCounter IIImplement an optimized version of the useCounter hook
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  • useCycleImplement a hook that cycles through a sequence of values
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  • Count ByImplement a function that counts the number of times a value appears in an array based on a function or property name
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  • CurryImplement a function that transforms a function that takes multiple arguments into a function that can be repeatedly called with only one argument at a time
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  • DebounceImplement a function to limit how many times a function can be executed by delaying the execution of the function until after a specified time after its last execution attempt
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  • PromisifyImplement a function that takes a function following the common error-first callback style and returns a version that returns promises
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  • ThrottleImplement a function to control the execution of a function by limiting how many times it can execute over time
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  • useArrayImplement a hook that manages an array of items
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  • useDebounceImplement a hook that debounces a value
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  • useSetImplement a hook that manages a JavaScript set
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  • useTimeoutImplement a hook that invokes a callback function after a specified delay
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  • useWindowSizeImplement a hook that returns the current height and width of the window
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  • ClassnamesImplement a function that conditionally joins CSS class names together
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  • Data MergingImplement a function to merge rows of data from the same user
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  • Event EmitterImplement a class that can subscribe to and emit events that trigger attached callback functions
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  • FlattenImplement a function that recursively flattens an array into a single level deep
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  • getElementsByStyleImplement a function to get all DOM elements that are rendered using the specified style
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  • HTML SerializerImplement a function to serialize an object into an HTML string with indentation
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  • JSON.stringifyImplement a function that converts a JavaScript value into a JSON string
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  • List FormatImplement a function that formats a list of items into a single readable string
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  • MemoizeImplement a function that returns a memoized version of a function which accepts a single argument
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  • MiddlewaresImplement a function that composes asynchronous middleware functions like in Koa.js
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  • Promise.allImplement the Promise.all() function that resolves to an array of results if all the input elements are resolved or rejects otherwise
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  • Promise.anyImplement the Promise.any() function that resolves when any of the input elements are resolved
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  • Squash ObjectImplement a function that returns a new object after squashing the input object into a single level of depth
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  • useInputControlImplement a hook that manages a controlled input value and tracks its dirty & touched state
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  • useMediaQueryImplement a hook that subscribes and responds to media query changes (e.g. screen size, resolution, orientation, etc.)
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  • useMediatedStateImplement a hook that is similar to useState, but supports a mediation process
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  • useQueryImplement a hook that manages a promise resolution
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  • Deep CloneImplement a function that performs a deep copy of a value
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  • Deep EqualImplement a function that determines if two values are equal
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  • getElementsByClassNameImplement a function to get all DOM elements that contain the specified classes
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  • Map Async LimitImplement a function that maps an array of items with an asynchronous mapping function while not exceeding the concurrency limit
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  • Deep OmitImplement a function that removes specified keys and their corresponding values from an object, including nested objects or arrays
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  • ClampPremiumImplement a function to clamp a number within the inclusive lower and upper bounds
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  • Function LengthPremiumImplement a function that returns the number of parameters expected by a function
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  • Number of ArgumentsPremiumImplement a function that returns the number of arguments it was called with
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  • SleepPremiumImplement a function that pauses for a specified duration before resuming execution
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  • Array.prototype.squarePremiumImplement a custom Array.prototype.square() method that squares the values in an array
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  • Cancellable IntervalPremiumImplement a function that acts like setInterval but returns a function to cancel the interval
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  • Cancellable TimeoutPremiumImplement a function that acts like setTimeout but returns a function to cancel the pending callback
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  • ChunkPremiumImplement a function that creates an array of elements split into smaller groups of a specified size
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  • CompactPremiumImplement a function that creates an array with all falsey values removed
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  • DifferencePremiumImplement a function that finds the difference in values between arrays
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  • Drop Right WhilePremiumImplement a function that excludes elements from the end of an array until the predicate returns false
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  • Drop WhilePremiumImplement a function that excludes elements from the beginning of an array until the predicate returns false
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  • FillPremiumImplement a function that fills an array with values within specified indices
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  • Find IndexPremiumImplement a function that returns the index of the first element in the array that satisfies the provided testing function
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  • Find Last IndexPremiumImplement a function that returns the index of the last element in the array that satisfies the provided testing function
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  • From PairsPremiumImplement a function that returns an object composed from key-value pairs
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  • Function.prototype.applyPremiumImplement the Function.prototype.apply() function that calls the function with a given `this` value and arguments as an array
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  • GetPremiumImplement a function to safely access deeply-nested properties in JavaScript objects
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  • In RangePremiumImplement a function to check if a number falls between two numbers
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  • IntersectionPremiumImplement a function that computes the intersection of arrays, returning a new array containing unique values present in all given arrays
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  • Max ByPremiumImplement a function that finds the maximum element based on the specified criteria
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  • Object MapPremiumImplement a function to transform values within an object
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  • OncePremiumImplement a function that accepts a callback and restricts its invocation to at most once
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  • Promise.rejectPremiumImplement a function to return a Promise object rejected with a reason
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  • RangePremiumImplement a function that returns a sequence of numbers in ascending order
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  • Range RightPremiumImplement a function that returns a sequence of numbers in descending order
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  • SingletonPremiumImplement a Singleton class that ensures a class has only one instance while providing a global point of access to that instance
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  • Unique ArrayPremiumImplement a function to remove all duplicate values from an array
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  • Array.prototype.atPremiumImplement the Array.prototype.at() method
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  • Array.prototype.filterPremiumImplement the Array.prototype.filter() method
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  • Array.prototype.mapPremiumImplement the Array.prototype.map() method
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  • ComposePremiumImplement a function that takes multiple functions as arguments and returns a new function that applies those functions in reverse
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  • Function.prototype.bindPremiumImplement the Function.prototype.bind() function that creates a new function with the `this` keyword set to a provided value
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  • jQuery.cssPremiumImplement a jQuery-like function that sets the style of a DOM element
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  • Promise.racePremiumImplement the Promise.race() function that resolves or rejects when any of the input elements are resolved or rejected
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  • SizePremiumImplement a function that returns the size of collection
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  • SumPremiumImplement a function that sums numbers by accepting a number and allows for repeated calling with more numbers until it is not called with any number
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  • useBoolean IIPremiumImplement an optimized version of the useBoolean hook
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  • useDefaultPremiumImplement a hook that returns the default value when state is null or undefined
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  • useEffectOncePremiumImplement a hook that runs an effect only once
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  • useFocusPremiumImplement a hook that enables programmatic focusing of an element
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  • usePreviousPremiumImplement a hook that returns the previous value of a state
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  • useStateWithResetPremiumImplement a hook that's similar to useState but with an additional reset function that resets the state to its initial value
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  • useTogglePremiumImplement a hook that manages a boolean toggle state
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  • Make Counter IIPremiumImplement a function that returns a counter object with methods to retrieve and manipulate the value
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  • Array.prototype.concatPremiumImplement the Array.prototype.concat() method
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  • Group ByPremiumImplement a function that groups values in an array based on a function or property name
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  • Intersection ByPremiumImplement a function that returns an array of unique values that are included in all given arrays based on a provided iteratee function
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  • Intersection WithPremiumComputes the intersection of arrays using a custom comparator function to determine equality between elements
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  • Is EmptyPremiumImplement a function to check if a value is an empty object, collection, map, or set
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  • LimitPremiumImplement a function that accepts a callback and restricts its invocation to at most N times
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  • Promise MergePremiumImplement a function to merge the results of two promises into a single value
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  • Promise.resolvePremiumImplement a function to resolve a given value to a Promise
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  • Promise TimeoutPremiumImplement a function that resolves a promise if it is fulfilled within a timeout period and rejects otherwise
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  • Promise.withResolversPremiumImplement a function that returns an object containing a new `Promise` object and two functions to resolve or reject it
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  • Promisify IIPremiumImplement a promisify function that allows the original function to override the return value
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  • TurtlePremiumImplement a Turtle class that moves a turtle on a 2D plane
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  • Union ByPremiumImplement a function that creates an array of unique values, in order, from all given arrays.
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  • useBreakpointPremiumImplement a hook that returns the current breakpoint name based on the current window width
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  • useClickOutsidePremiumImplement a hook that detects clicks outside of a specified element
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  • useCountdownPremiumImplement a hook that manages a countdown
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  • useEventListenerPremiumImplement a hook that subscribes to browser events
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  • useHoverPremiumImplement a hook that tracks whether an element is being hovered
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  • useIntervalPremiumImplement a hook that creates an interval that invokes a callback function at a specified delay
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  • useKeyPressPremiumImplement a hook that subscribes to keyboard events
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  • useMapPremiumImplement a hook that manages a JavaScript map
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  • useObjectPremiumImplement a hook that manages an object value
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  • useStepPremiumImplement a hook that manages a step counter for a multi-step process
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  • useThrottlePremiumImplement a hook that throttles a value
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  • Camel Case KeysPremiumImplement a function to convert all the keys in an object to camel case
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  • Compact IIPremiumImplement a function that returns an object with all falsey values removed
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  • Conforms ToPremiumImplement a function that checks if object conforms to source
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  • Curry IIPremiumImplement a function that transforms a function that takes multiple arguments into a function that can be repeatedly called with any number of arguments
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  • Debounce IIPremiumImplement a debounce function that comes with a cancel method to cancel delayed invocations and a flush method to immediately invoke them
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  • Event Emitter IIPremiumImplement a class that can subscribe to and emit events that trigger attached callback functions. Subscription objects are returned and can unsubscribe itself
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  • getElementsByTagNamePremiumImplement a function to get all DOM elements that match a tag
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  • Identical DOM TreesPremiumImplement a function to determine if two DOM trees are the same
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  • jQuery Class ManipulationPremiumImplement a set of jQuery-like functions that manipulates classes on a DOM element
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  • Map AsyncPremiumImplement a function that maps an array of items with an asynchronous mapping function
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  • Promise.allSettledPremiumImplement the Promise.allSettled() function that resolves to an array of outcomes when all the input elements are either resolved or rejected
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  • Resumable IntervalPremiumImplement a function that creates a resumable interval object
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  • Text SearchPremiumImplement a function to highlight text if a searched term appears within it
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  • useIdlePremiumImplement a hook that detects user inactivity
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  • Deep MapPremiumImplement a function to recursively transform values
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  • Text Search IIPremiumImplement a function to highlight text if searched terms appear within it
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  • Deep MergePremiumImplement a function that merges two objects together
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  • Memoize IIPremiumImplement a function that returns a memoized version of a function which accepts any number of arguments
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  • Curry IIIPremiumImplement a function which transforms a function which takes variadic arguments into a function that can be repeatedly called with any number of arguments
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  • Classnames IIPremiumImplement a function that conditionally joins CSS class names together and also handles de-duplication and function values
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  • Backbone ModelPremiumImplement a class resembling Backbone.Model which allows storing of attributes/values and responding to changes in specific attribute values
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  • Data SelectionPremiumImplement a function to filter rows of data matching a specified requirement
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  • getElementsByTagNameHierarchyPremiumImplement a function to get all DOM elements that match a tag hierarchy
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  • Table of ContentsPremiumImplement a function to construct a table of contents from an HTML document
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  • Deep Clone IIPremiumImplement a function that performs a deep copy of a value, but also handles circular references
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  • JSON.stringify IIPremiumImplement a function that converts a JavaScript value into a JSON string
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