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 |
fasdfdsfsfads sd s fdsfd |
| 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) |
The value of the first element satisfying the test. |
| arr.findIndex(fn) |
The index of the first element satisfying the test. |
| arr.indexOf(item) |
Returns irst index of item (or -1 if not found). |
| arr.lastIndexOf(item) |
Like indexOf, but searching backward from the end. |
| arr.join(separator) |
Returns a new string by concatenating items. |
| arr.toString() |
Returns a new string, separated by commas. |
| 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 at the end. |
(Warning: Careful with modifications when using React state 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
|
|
| 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(arg1, arg2,…) |
Creates a new Array from a variable number of arguments. |
Array methods that return iterators
|
|
| 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. |
React Academy
To get the latest version of this document, visit the handout section of ReactAcademy.live.
