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@just-boris
Created October 13, 2020 09:05
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Nested weak map
import { NestedWeakMap } from './nested-weak-map';
const key1 = {};
const key2 = {};
const map = new NestedWeakMap();
map.get([key1, key2]); // undefined
map.getOrCreate([key1, key2], () => 'default'); // "default"
map.get([key1, key2]); // "default"
export class NestedWeakMap<T> {
private content = new WeakMap<any, any>();
get(keys: object[]): T | undefined {
let current: any = this.content;
for (const key of keys) {
current = current.get(key);
if (!current) {
return;
}
}
return current;
}
set(keys: object[], value: T) {
let current = this.content;
const initialKeys = keys.slice(0, -1);
const last = keys[keys.length - 1];
for (const key of initialKeys) {
let next = current.get(key);
if (!next) {
next = new WeakMap();
current.set(key, next);
}
current = next;
}
current.set(last, value);
}
getOrCreate(keys: object[], getDefaultValue: () => T) {
let value = this.get(keys);
if (!value) {
value = getDefaultValue();
this.set(keys, value);
}
return value;
}
}
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