ring buffer...

RingBuffer.ts

import {assert} from 'chai';

/**
 * Implement a class named ring buffer with fixed capacity such that
 * 
 * constructor: takes the capacity for the ring buffer
 *
 * push: adds a value to the ring buffer.
 * pop: removes the last value from the ring buffer or undefined if it's empty.
 * peek: returns the current value of the most recent value added or undefined if none have been added
 * 
 * If we have too many values (exceeding capacity) the oldest values are lost. 
 *
 * The ordering of the push operations must be kept.
 */
class RingBuffer<T> extends Array {
    peek() {
        return this[this.length - 1];
    }
}

// the following tests must pass
describe("RingBuffer", function() {

    it("basic", function() {
  
        const rb = new RingBuffer<number>(3);
  
        assert.isUndefined(rb.peek());
  
        rb.push(1);
        assert.isEqual(rb.peek(), 1);

        assert.isEqual(rb.pop(), 1);

        assert.isUndefined(rb.peek());
  
    });
  
    it("lost data", function() {
      
        const rb = new RingBuffer<number>(3);
        rb.push(1);
        rb.push(2);
        rb.push(3);
        rb.push(4);
      
        assert.isEqual(rb.pop(), 4);
        assert.isEqual(rb.pop(), 3);
        assert.isEqual(rb.pop(), 2);
        assert.isUndefined(rb.pop());
      
    });

));