advanced-map-initialized/index.js

Map-like class with default values

"use strict";
const tslib_1 = require("tslib");
const advanced_map_base_1 = tslib_1.__importDefault(require("advanced-map-base"));
/**
 * Objects of this class call their `init` function
 * every time`get()`is invoked upon non-existing key.
 * As a result, `get()` never return `undefined`.
 */
class Initialized extends advanced_map_base_1.default {
    /**
     * @param Map A constructor (a.k.a class) that creates a Map-like object.
     * @param init Function that takes a yet-to-initialized key and returns default value.
     */
    constructor(Map, init) {
        super(Map);
        this.init = init;
    }
    /**
     * Check if a certain key is initialized/set.
     * @returns `true` if given key is initialized or set, `false` otherwise.
     */
    has(key) {
        return this.data.has(key);
    }
    /**
     * If `key` exists, return corresponding value.
     * Otherwise, call `init` function and add its returning value to the map.
     * @param key Map's key.
     * @returns Corresponding value.
     */
    get(key) {
        const { data } = this;
        if (data.has(key))
            return data.get(key);
        const value = this.init(key);
        data.set(key, value);
        return value;
    }
    /**
     * Set `key` to point to `value`.
     * @param key Key.
     * @param value Value.
     */
    set(key, value) {
        this.data.set(key, value);
        return this;
    }
    /**
     * Delete a key if it exists.
     * @param key Key to be deleted.
     * @returns `true` if deleted key existed and `false` otherwise.
     */
    delete(key) {
        return this.data.delete(key);
    }
}
module.exports = Initialized;
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