Design Dynamic Array (Resizable Array) https://neetcode.io/problems/dynamicArray

dynamicarr.js

class DynamicArray {
    /**
     * @constructor
     * @param {number} capacity
     */
    constructor(capacity) {
        this.data = new Array(capacity);
        this.num_elements = 0;
    }

    /**
     * @param {number} i
     * @returns {number}
     */
    get(i) {
        return this.data[i];
    }

    /**
     * @param {number} i
     * @param {number} n
     * @returns {void}
     */
    set(i, n) {
        this.data[i] = n;
    }

    /**
     * @param {number} n
     * @returns {void}
     */
    pushback(n) {
        if (this.num_elements === this.data.length) {
            this.resize();
        }

        this.set(this.num_elements++, n);
    }

    /**
     * @returns {number}
     */
    popback() {
        const val = this.get(this.num_elements - 1);
        this.set(this.num_elements - 1, undefined);
        this.num_elements--;

        return val;
    }

    /**
     * @returns {void}
     */
    resize() {
        const newArr = new Array(this.data.length * 2);

        for (let i=0; i<this.data.length; i++) {
            newArr[i] = this.get(i);
        }

        this.data = newArr;
    }

    /**
     * @returns {number}
     */
    getSize() {
        return this.num_elements;
    }

    /**
     * @returns {number}
     */
    getCapacity() {
        return this.data.length;
    }
}