CircularBuffer class

CircularBuffer-v1.js

/**
 * Implement Circular/Ring Buffer basic behaviour.
 *
 * @version 1
 *
 * @example
 * const buffer = new CircularBuffer(3);
 *
 * buffer.list(); // []
 * buffer.push('URL 1');
 * buffer.push('URL 2');
 * buffer.push('URL 3');
 * buffer.list(); // ['URL 1', 'URL 2', 'URL 3']
 * [...buffer]; // ['URL 1', 'URL 2', 'URL 3'] => buffer is iterable
 * buffer.push('URL 4');
 * buffer.list(); // ['URL 2', 'URL 3', 'URL 4'] => oldest entry dropped
 */
class CircularBuffer {
    #data;

    constructor ( length ) {
        this.#data = [];
        Object.defineProperty(this, 'length', {
            value: length
        });
    }

    push ( value ) {
        if ( value != undefined ) {
            if ( this.#data.length + 1 > this.length ) {
                this.#data.shift();
            }

            this.#data.push(value);
        }
    }

    list () {
        return this.#data;
    }

    *[Symbol.iterator]() {
        for (let index = 0; index < this.#data.length; yield this.#data[index++]);
    }
}

CircularBuffer-v2.js

/**
 * Implement Circular/Ring Buffer basic behaviour.
 * Read/write operations are done with O(1) complexity.
 *
 * @version 2
 *
 * @example
 * const buffer = new CircularBuffer(3);
 *
 * buffer.list(); // []
 * buffer.write('URL 1');
 * buffer.write('URL 2');
 * buffer.write('URL 3');
 * buffer.list(); // ['URL 1', 'URL 2', 'URL 3']
 * [...buffer]; // ['URL 1', 'URL 2', 'URL 3'] => buffer is iterable
 * buffer.write('URL 4');
 * buffer.list(); // ['URL 4', 'URL 2', 'URL 3'] => oldest entry dropped
 */
class CircularBuffer {
    #data;
    #readPointer;
    #writePointer;

    constructor ( length ) {
        this.#data = [];
        this.#readPointer = 0;
        this.#writePointer = 0;
        Object.defineProperty(this, 'length', {
            value: length
        });
    }

    read () {
        const result = this.#data[this.#readPointer];
        this.#readPointer = (this.#readPointer + 1) % this.length;

        return result;
    }

    write ( value ) {
        this.#data[this.#writePointer] = value;
        this.#writePointer = (this.#writePointer + 1) % this.length;
    }

    list () {
        return this.#data;
    }

    *[Symbol.iterator]() {
        for (let index = 0; index < this.#data.length; yield this.#data[index++]);
    }
}