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Map.md

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Map

Extended Map utilities plus callable and readonly wrappers.

Import

import { DataMap, ReadonlyMap, map } from '@stackpress/lib';

When To Use It

Use DataMap when you want native Map semantics with collection helpers. Use ReadonlyMap when a consumer should not mutate the store. Use map() when you want a callable getter plus Map methods on one value.

API

Constructor

const users = new DataMap<string, number>([
  ['ada', 1],
  ['grace', 2]
]);

ReadonlyMap takes the same entry-array shape.

DataMap Methods

Method Returns Notes
filter(callback) new DataMap subclass Filters entries by value and key.
find(callback) [K, V] | undefined First matching entry.
findKey(callback) K | undefined First matching key.
findValue(callback) V | undefined First matching value.
first() V | undefined Alias for index(0).
index(index) V | undefined Value by insertion order.
last() V | undefined Value at size - 1.
map(callback) new DataMap<K, T> Maps values while preserving keys.
toArray() V[] Values only.
toObject() Record<string, V> Converts entries to a plain object.
toString(replacer?, space?) string JSON string of toObject().

ReadonlyMap Methods

ReadonlyMap exposes read and transform helpers over an internal DataMap:

  • entries()
  • filter(callback)
  • find(callback)
  • findKey(callback)
  • findValue(callback)
  • forEach(iterator)
  • get(key)
  • has(key)
  • keys()
  • map(callback)
  • size
  • toObject()
  • toString(replacer?, space?)
  • values()

Callable Helper

const headers = map<string, string>();

headers.set('content-type', 'application/json');
headers('content-type');
headers.get('content-type');

map(data?) returns a callable CallableMap<K, V>. It supports normal DataMap methods and a getter function signature.

Example

import { DataMap } from '@stackpress/lib';

const scores = new DataMap<string, number>();
scores.set('one', 1);
scores.set('two', 2);
scores.set('three', 3);

const passing = scores.filter(value => value >= 2);
const first = scores.first();
const serialized = scores.toString();

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