Module scope

Unique value allocation.

Provides Scope, a counter that hands out unique sequential ids. Each id is cached against a caller-supplied key, compared by reference identity, so repeated lookups of the same key resolve to the same value without a string proxy.

By default createScope builds a scope handing out raw numeric ids; given a mapper, each id is passed through it to produce the value returned instead.

import { createScope } from '@metreeca/core/scope';

const scope = createScope();
const node = {};

scope.resolve(node); // 0 (fresh id bound to node)
scope.resolve(node); // 0 (cached hit on the same reference)
scope.resolve({});   // 1 (unique reference, fresh id)
scope.resolve();     // 2 (anonymous, always fresh)
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Passing a mapper derives a value from each id, caching it and returning it again for repeated keys:

const labels = createScope(id => `?v${id}`);

labels.resolve(node); // "?v0"
labels.resolve(node); // "?v0" (cached hit)
labels.resolve();     // "?v1"
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Passing several keys forms a composite: the value is shared only when every component matches by reference, in the same order.

const edges = createScope();
const from = {};
const to = {};

edges.resolve(from, to); // 0 (fresh id bound to the pair)
edges.resolve(from, to); // 0 (cached hit on the same pair)
edges.resolve(to, from); // 1 (order matters)
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