index.js

// Copyright (c) 2023 by Shakhbozbek Usmonov Miracle Programmer.
// leetcode.com 30 Days of JavaScript challenge

// ----- Started -----

class Calculator {
    /**
     * @param {number} value
     */
    constructor(value) {
        this.result = value;
    }

    /**
     * @param {number} value
     * @return {Calculator}
     */
    add(value) {
        this.result += value;
        return this;
    }

    /**
     * @param {number} value
     * @return {Calculator}
     */
    subtract(value) {
        this.result -= value;
        return this;
    }

    /**
     * @param {number} value
     * @return {Calculator}
     */
    multiply(value) {
        this.result *= value;
        return this;
    }

    /**
     * @param {number} value
     * @return {Calculator}
     */
    divide(value) {
        if (value === 0) throw new Error("Division by zero is not allowed");
        this.result /= value;
        return this;
    }

    /**
     * @param {number} value
     * @return {Calculator}
     */
    power(value) {
        this.result **= value;
        return this;
    }

    /**
     * @return {number}
     */
    getResult() {
        return this.result;
    }
}

//----------------------------------------------------------------

/**
 * @param {any[]} arr
 * @param {number} depth
 * @return {any[]}
 */
var flat = function (arr, n) {
    const stack = [...arr.map((item) => [item, n])];
    const result = [];

    while (stack.length > 0) {
        const [item, n] = stack.pop();

        if (Array.isArray(item) && n > 0) {
            stack.push(...item.map((subItem) => [subItem, n - 1]));
        } else {
            result.push(item);
        }
    }
    return result.reverse();
};

//----------------------------------------------------------------

/**
 * @param {Object|Array} obj
 * @return {Object|Array}
 */
var compactObject = function (obj) {
    if (obj === null) return null;
    if (Array.isArray(obj)) return obj.filter(Boolean).map(compactObject);
    if (typeof obj !== "object") return obj;

    const compacted = {};
    for (const key in obj) {
        let value = compactObject(obj[key]);
        if (Boolean(value)) compacted[key] = value;
    }

    return compacted;
};

//----------------------------------------------------------------

class EventEmitter {
    events = {};
    subscribe(event, cb) {
        this.events[event] = this.events[event] || [];
        this.events[event].push(cb);
        return {
            unsubscribe: () => {
                this.events[event] = this.events[event].filter(
                    (fn) => fn !== cb
                );
            },
        };
    }

    emit(event, args = []) {
        const result = [];
        if (this.events[event]) {
            for (let fn of this.events[event]) {
                result.push(fn(...args));
            }
        }
        return result;
    }
}

/**
 * const emitter = new EventEmitter();
 *
 * // Subscribe to the onClick event with onClickCallback
 * function onClickCallback() { return 99 }
 * const sub = emitter.subscribe('onClick', onClickCallback);
 *
 * emitter.emit('onClick'); // [99]
 * sub.unsubscribe(); // undefined
 * emitter.emit('onClick'); // []
 */

//----------------------------- END ----------------------------------------------------------------