Transforming

Methods that produce a new array from an existing one. Lambdas use the arrow form param -> expression. Any function value works as a callback, including typed lambdas like (number x) number -> x * 2 and named functions.

.map(fn) → array

Applies fn to every element and collects the results.

log [1, 2, 3].map(x -> x * 2)  // [2, 4, 6]

.filter(fn) → array

Keeps only the elements for which fn returns true.

log [1, 2, 3, 4].filter(x -> x > 2)  // [3, 4]

.sort() → array

Returns the elements sorted ascending.

.sortBy(key) → array

Sorts an array of objects by the named field. Pass "descending" as a second argument to reverse.

arr = [{name: "bob", age: 30}, {name: "alice", age: 25}]
log arr.sortBy("age").getKeys("name")               // ["alice", "bob"]
log arr.sortBy("age", "descending").getKeys("name") // ["bob", "alice"]

.sortBy(fn) also accepts an arrow function that returns the value to sort on.

.reverse() → array

Returns the elements in reverse order.

log [3, 1, 2].sort().reverse()  // [3, 2, 1]

.deDupe() → array

Removes duplicate values, keeping first occurrences.

log [1, 2, 2, 3, 1, 4].deDupe()  // [1, 2, 3, 4]

.fill(value) → array

Returns an array of the same length with every element set to value.

log (1 to 3).fill("hi")  // ["hi", "hi", "hi"]

.concat(other) → array

Returns a new array with other appended. (Non-mutating; ++ does the same.)

log [1, 2, 3].concat([4, 5, 6])  // [1, 2, 3, 4, 5, 6]