armita (array methods for iterators) re-implements Javascript array methods for iterator objects.
// iterate a Map
let m = new Map([
['a', 10],
['b', 20],
['c', 30],
]);
found = m.values().filter(val => val >= 15)
// process a big array without creating intermediate temp arrays
let result = bigArray
.values()
.map(x => x.toUpperCase())
.filter(x => x.includes('AHA')
.map(x => '<b>' + x + '</b>')
.join('\n')
// lazily compute a heavy function and stop once the result is found
let result = bigArray
.values()
.map(heavyFunction)
.find(result => result > 100);
// slice from an endless generator
function* fibs() {
let [a, b] = [0, 1];
while (true) {
yield a;
[a, b] = [b, a + b];
}
}
let first50fibs = fibs().slice(0, 50);armita reimplements all array methods (as of ES2019), except mutarors (push, splice and friends).
Array construction methods (like .map), return a generator in armita.
"Greedy" means that a method unconditionally consumes this iterator, "lazy" means a method reads from it on demand.
| method | returns | greedy/lazy |
|---|---|---|
concat(...values) |
generator |
lazy |
entries() |
generator |
lazy |
every(fn, thisArg?) |
bool |
lazy |
filter(fn, thisArg?) |
generator |
lazy |
find(fn, thisArg?) |
any |
lazy |
findIndex(fn, thisArg?) |
int |
lazy |
flat(depth?) |
generator |
lazy |
flatMap(fn, thisArg?) |
generator |
lazy |
forEach(fn, thisArg?) |
void |
lazy |
includes(value, fromIndex?) |
bool |
lazy (greedy when a negative fromIndex is given) |
indexOf(value, fromIndex?) |
int |
lazy (greedy when a negative fromIndex is given) |
join(separator?) |
string |
greedy |
keys() |
generator |
lazy |
lastIndexOf(value, fromIndex?) |
int |
greedy |
map(fn, thisArg?) |
generator |
lazy |
reduce(fn, init?) |
any |
lazy |
reduceRight(fn, init?) |
any |
greedy |
slice(begin?, end?) |
generator |
lazy (greedy when negative begin and/or end indexes are given) |
some(fn, thisArg?) |
bool |
lazy |
toLocaleString() |
string |
greedy |
toString() |
string |
greedy |
values() |
generator |
lazy |
npm install armita
- async generators?
.d.ts