StringSet implementation

string-set.js

const StringSetBase = require("./string-set-base");

class StringSet extends StringSetBase {

    constructor() { 
        super();
        this.stringSet = new Set();
    }

    /**
     * Adds a new element to the set
     * @param {String} element
     */
    add(element) { 
        if (typeof element !== 'string') {
            throw new TypeError("StringSet.add(element) only accepts a single input string");
        }
        this.stringSet.add(element); 
    }

    /**
     * Removes and element from the set
     * @param {String} element
     */
    remove(element) { 
        if (typeof element !== 'string') {
            throw new TypeError("StringSet.remove(element) only accepts a single input string");
        }
        this.stringSet.delete(element);
    }

    /**
     * Decides if element is part of the set
     * @param {String} element
     * @return {Boolean}
     */
    contains(element) { 
        if (typeof element !== 'string') {
            throw new TypeError("StringSet.contains(element) only accepts a single input string");
        }
        return this.stringSet.has(element); 
    }
    
}

module.exports = StringSet;

string-set.spec.js

const StringSet = require('../skawa/string-set/string-set');

describe('StringSet', () => {

    let mySet;

    beforeEach(function () {
        mySet = new StringSet();
    });

    it('should not contain any given element by default', function () {
        expect(mySet.contains('abrakadabra')).toBeFalsy("Should not contain 'abrakadabra' by default");
    });

    it('should contain a given element after add()', function () {
        expect(mySet.contains('abrakadabra')).toBeFalsy("Should not contain 'abrakadabra' by default");
        mySet.add('abrakadabra');
        expect(mySet.contains('abrakadabra')).toBeTruthy("Should contain 'abrakadabra' after calling add()");
    });

    it('should add and remove elements only once', function () {
        expect(mySet.contains('abrakadabra')).toBeFalsy("Should not contain 'abrakadabra' by default");
        mySet.add('abrakadabra');
        mySet.add('abrakadabra');
        expect(mySet.contains('abrakadabra')).toBeTruthy("Should contain 'abrakadabra' after calling add()");
        mySet.remove('abrakadabra');
        expect(mySet.contains('abrakadabra')).toBeFalsy("Should not contain 'abrakadabra' after calling remove()");
    });

    it('should not accept non-string values', function () {
        try {
            mySet.add(42);
            fail('should throw an exception when adding non-string values');
        } catch (exception) {
            expect(exception.message).toEqual('StringSet.add(element) only accepts a single input string');
        }
    });

    it('should not check for non-string values', function () {
        try {
            mySet.contains(false);
            fail('should throw an exception when checking for non-string values')
        } catch (exception) {
            expect(exception.message).toEqual('StringSet.contains(element) only accepts a single input string');
        }
    });

    it('should not try to remove non-string values', function () {
        try {
            mySet.remove(undefined);
            fail('should throw an exception when trying to remove non-string values');
        } catch (exception) {
            expect(exception.message).toEqual('StringSet.remove(element) only accepts a single input string');
        }
    });

});