Array and object methods, iteration, and manipulation in JavaScript.
41 cards · basic cards · AI-written, checked twice. Edit anything.
- What does Array.push() do?
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Adds one or more elements to the end of an array and returns the new length. Mutates the original array.- What does Array.pop() do?
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Removes the last element from an array and returns that element. Mutates the original array. Returns undefined if array is empty.- What does Array.shift() do?
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Removes the first element from an array and returns that element. Mutates the original array. Returns undefined if array is empty.- What does Array.unshift() do?
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Adds one or more elements to the beginning of an array and returns the new length. Mutates the original array.- What does Array.slice() do?
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Returns a shallow copy of a portion of an array. Does not mutate the original array. Takes start and end indices.- What does Array.splice() do?
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Removes elements from an array and optionally inserts new elements. Mutates the original array and returns an array of removed elements.- What does Array.concat() do?
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Combines two or more arrays into a new array. Returns a new array and does not mutate the originals.- What does Array.join() do?
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Combines all array elements into a single string, separated by a specified separator. Default separator is comma.- What does Array.indexOf() do?
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Returns the index of the first element that matches the search value. Returns -1 if not found.- What does Array.includes() do?
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Checks whether an array contains a specified element and returns a boolean. More readable than indexOf for simple presence checks.- What does Array.reverse() do?
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Reverses the order of elements in an array in place. Mutates the original array and returns a reference to it.- What does Array.sort() do?
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Sorts elements in an array in place. By default sorts lexicographically as strings. Takes optional comparison function.- What does Array.map() do?
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Transforms each element in an array using a callback function and returns a new array. Does not mutate the original array.- What does Array.filter() do?
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Creates a new array with elements that pass the test in the callback function. Does not mutate the original array.- What does Array.reduce() do?
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Accumulates array elements into a single value by applying a callback function. Takes a callback and optional initial value.
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