Module arrays

General-purpose array operations.

Normalising a Value to an Array

Coerce an optional, single or multi-valued input into an array for uniform iteration:

import { some } from '@metreeca/core/arrays';

some(undefined);           // []
some("x");                 // ["x"]
some(["x", "y"]);          // ["x", "y"]
some(new Set(["x", "y"])); // ["x", "y"]
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Retaining Unique Values

Keep the unique values of a collection, dropping later duplicates:

import { unique } from '@metreeca/core/arrays';

unique([1, 1, 2, 3, 3]);      // [1, 2, 3]
unique(new Set([1, 2]));      // [1, 2]
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Combining Collections

Merge several collections into their union, narrow them to their shared intersection, or subtract the later ones from the first, deduplicating in every case:

import { difference, intersection, union } from '@metreeca/core/arrays';

union([[1, 2], [2, 3]]);              // [1, 2, 3]
intersection([[1, 2, 3], [2, 3, 4]]); // [2, 3]
difference([[1, 2, 3], [2, 3, 4]]);   // [1]
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Expecting a Cardinality

Reduce an optional, single or multi-valued input to the number of values a call site expects, failing at the boundary when the input doesn't match:

import { multiple, optional, required } from '@metreeca/core/arrays';

required(["x"]);      // "x"
required(["x", "y"]); // TypeError
optional(undefined);  // undefined
optional(["x", "y"]); // TypeError
multiple("x");        // ["x"]
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