JavaScript
JS arrays cheat sheet
Array and object helpers in modern JavaScript, including the non-mutating copies added in ES2023 and grouping helpers, with notes on which methods mutate.
Create
Access
Transform
Immutable
Objects
Things worth remembering
- sort, reverse, splice, push and fill mutate. toSorted, toReversed, toSpliced and with return copies.
- sort() compares strings by default, so [10, 9].sort() gives [10, 9]. Always pass a comparator for numbers.
- Array.from({ length: n }, mapFn) is the cleanest way to build a range without a loop.