Array methods that return a new array
| a | a |
|---|---|
| arr.concat(arg1, arg2,…) | Creates an array with new things at the end. |
| arr.slice(start, end) | Creates a subarray. |
| arr.filter(fn) | Creates a new array with all items that pass the test. |
| arr.flat(depth) | Creates an array with all sub-arrays flattened to the specified depth. Depth 1: [1, [2, 3], [4, 5, [6]]] -> [1,2,3,4,5,[6]]. |
| arr.map(fn) | Creates array with the results of fn on every item. |
| arr.flatMap(fn) | Creates array by first doing a map(fn), then a flat(1). |
Array methods that return one value
| a | a |
|---|---|
| arr.every(fn) | Returns true if all elements in array pass the test. |
| arr.some(fn) | Returns true if at least one item passes the test. |
| arr.includes(item) | Determines if array includes a certain item. |
| arr.find(fn) | Returns the value of the first element satisfying the test. |
| arr.findIndex(fn) | Returns the index of the first element satisfying the test. |
| arr.indexOf(item) | Returns the first index of item (or -1 if not found). |
| arr.lastIndexOf(item) | Like indexOf, but searching backward from the end. |
| arr.at(pos) | Returns item from nth position. If negative, starts from the end. arr.at(-1) returns last item. |
| arr.join(separator) | Returns a new string by concatenating items, separated by commas (or separator). |
| arr.toString() | Returns a string representation of the array. |
| arr.toLocaleString (locales, options) |
Returns a new string, using toLocaleString. |
| arr.reduce(fn) | Execute fn on each item, resulting in a single output. |
| arr.reduceRight(fn) | Like reduce(), but starting from the end. |
(Warning: Careful with modifications when using React state, reducer, or Redux store. If you must, use the following methods on a cloned state, not the state itself. Or use ImmerJS.)
Array methods that modify the array
| a | a |
|---|---|
| arr.push(...items) | Adds items to the end, returns size of array. |
| arr.pop() | Removes an item from the end, returns it. |
| arr.shift() | Removes an item from the beginning, returns it. |
| arr.unshift(...items) | Adds items to the beginning, returns size of array. |
| arr.splice(start, deleteCount, …items) |
Removes items in the middle, adds items, returns an array containing the deleted elements. |
| arr.copyWithin (target, start, end) |
Copies part of an array to another location in the same array, without changing size, returns the array. |
| arr.fill(value, start, end) | Fills all the elements of an array from a start index to an end index with a static value, returns the array. |
| arr.reverse() | Reverses an array in place, returns the array. |
| arr.sort(fn) | Sorts the elements of an array in place, returns the array. |
Static Array methods (helpers to create new Arrays)
| a | a |
|---|---|
| Array.from (arr, mapfn) |
Creates a new, shallow-copied Array instance from an array-like or iterable object. Second param is a map function. |
| Array.of (a1, a2, …) |
Creates a new Array from a variable number of arguments. |
Array methods that return iterators
| a | a |
|---|---|
| arr.entries() | Returns an Array Iterator containing key/value pairs. |
| arr.keys() | Returns an Array Iterator containing keys. |
| arr.values() | Returns an Array Iterator containing values. |
Array methods that return nothing
| a | a |
|---|---|
| arr.forEach(fn) | Executes fn once for each array element. |
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