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fbfreitas edited this page Oct 8, 2026 · 5 revisions
Instituto Superior de Engenharia de Lisboa
Bachelor in Computer Science and Computer Engineering
Bachelor in Informatics, Networks and Telecommunications Engineering
Web Programming and Architecture/ Introduction to Web Programming
Winter Semester of 2026/2027 – 1st practical assignment

Delivery

This first practical assignment has 2 parts, and it should be implemented and delivered individually by each student in the individual submission repository (created by the teacher).

The delivery dates are the following:

Starter project and tests

The Part 1 starter project is provided in the next repository: https://github.com/isel-leic-ipw/apw-2627-a1-template

It contains one source file per exercise and example tests for Exercises 1 and 2. Install its dependencies and run the tests with:

npm install
npm test

The supplied tests are expected to fail until the corresponding functions are implemented. Students must create equivalent tests for Exercises 3, 4, and 5 and add further tests for Exercises 1 and 2.

Part 1 - JavaScript Functions

Implement the following JavaScript functions and create tests that confirm the described behavior:

Exercise 1 – Validate Array Elements

Objective: Write a function validateArrayElements(arr, elementValidator) that validates each element of an array using a given validation function.

Requirements:

  • Return an array of objects.
  • Each object should have:
  • value: the original element
  • isValid: a boolean indicating whether the element passed the validation

Examples:

Numbers:

const numbers = [2, 3, 4, 5];
console.log(validateArrayElements(numbers, n => n % 2 === 0));
/*
[
 { value: 2, isValid: true },
 { value: 3, isValid: false },
 { value: 4, isValid: true },
 { value: 5, isValid: false }
]
*/

Objects:

const products = [
 { name: "Laptop", category: "Electronics" },
 { name: "Shirt", category: "" },
 { name: "Chair", category: "Furniture" }
];
console.log(validateArrayElements(products, p => p.category.length > 0));
/*
[
 { value: { name: "Laptop", category: "Electronics" }, isValid: true },
 { value: { name: "Shirt", category: "" }, isValid: false },
 { value: { name: "Chair", category: "Furniture" }, isValid: true }
]
*/

Exercise 2 – Validate and Correct Array

Objective: Write a function validateAndCorrectArray(arr, elementValidator, defaultValue) that returns an object containing:

  1. correctedArray: array with invalid elements replaced by defaultValue
  2. invalidElements: array of the original invalid elements

Requirements:

  • Use the function from Exercise 1 to validate each element only once.

Examples:

Numbers:

const numbers = [2, 3, 4, 5];
const result = validateAndCorrectArray(numbers, n => n % 2 === 0, 0);


console.log(result.correctedArray);  // [2, 0, 4, 0]
console.log(result.invalidElements); // [3, 5]

Objects:

const products = [
 { name: "Laptop", category: "Electronics" },
 { name: "Shirt", category: "" },
 { name: "Chair", category: "Furniture" }
];
const defaultProduct = { name: "Unknown", category: "Misc" };
const resultProducts = validateAndCorrectArray(products, p => p.category.length > 0, defaultProduct);


console.log(resultProducts.correctedArray);
/*
[
 { name: "Laptop", category: "Electronics" },
 { name: "Unknown", category: "Misc" },
 { name: "Chair", category: "Furniture" }
]
*/
console.log(resultProducts.invalidElements);
/*
[
 { name: "Shirt", category: "" }
]
*/

Additional test cases

The provided tests cover only the examples above. Add tests for cases such as:

  • Exercise 1: an empty array; validators that accept all or reject all elements; arrays containing values of different types; and verification that the validator is called once per element.
  • Exercise 2: an empty array; arrays where all elements are valid or invalid; primitive and object default values; and verification that each element is validated only once.

Also create tests for all the requirements of Exercises 3, 4, and 5, including relevant edge cases.

Exercise 3 – partitionBy

Objective: Write a function partitionBy(array, predicate) that splits an array into two arrays:

  • The first contains all elements that satisfy the predicate.
  • The second contains all elements that do not satisfy the predicate.

Examples:

Numbers:

const numbers = [1, 2, 3, 4, 5, 6];
const [evens, odds] = partitionBy(numbers, n => n % 2 === 0);
console.log(evens); // [2, 4, 6]
console.log(odds);  // [1, 3, 5]

Objects:

const users = [
   { name: "Alice", age: 25 },
   { name: "Bob", age: 17 },
   { name: "Charlie", age: 30 }
];
const [adults, minors] = partitionBy(users, u => u.age >= 18);
console.log(adults);
/*
[
 { name: "Alice", age: 25 },
 { name: "Charlie", age: 30 }
]
*/
console.log(minors);
/*
[
 { name: "Bob", age: 17 }
]
*/

Hint: You can use reduce to build both arrays in a single pass.

Exercise 4 – checkItemsExist

Objective: Implement checkItemsExist(validItems, key) that returns a function. The returned function takes an array of items and returns true if all items exist in validItems based on the given key, otherwise false.

Examples:

Products:

const validProducts = [
   { sku: "A123", name: "Laptop" },
   { sku: "B456", name: "Mouse" },
   { sku: "C789", name: "Keyboard" }
];


const checkProducts = checkItemsExist(validProducts, "sku");


console.log(checkProducts([{ sku: "A123" }, { sku: "B456" }])); // true
console.log(checkProducts([{ sku: "A123" }, { sku: "X999" }])); // false

Hint:

  • Use map to extract the valid keys.
  • Use every and includes to check if all items exist.

Exercise 5 – timeExecution

Objective: Create a function timeExecution(object, method) that overrides a specified method of an object to measure and log the time it takes to execute.

Requirements:

  • The original method should still behave as before.
  • Every time the method is called, log the execution time in milliseconds.

Example:

const obj = {
   compute(x) {
       return x * 2; // simplified computation
   }
};


timeExecution(obj, 'compute');
console.log(obj.compute(5)); // Logs execution time, e.g, returns 10
console.log(obj.compute(10)); // Logs execution time, e.g, returns 20

Hint:

  • Use performance.now() (or Date.now()) to measure time.
  • Use apply to call the original method with the correct context and arguments.

Part 2 - Node application

Foreword

This part requires your code to make HTTP requests to the RAWG Video Games Database API.

Each student must obtain an API key from the RAWG API page. The key must be included in the key query parameter of every HTTP request. For example:

https://api.rawg.io/api/games/3498?key=YOUR_API_KEY

The API key must not be hard-coded in the source code or committed to the repository. Read it from an environment variable instead. Be sure you understand and comply with the API terms and request limits.

Application requirements

The application reads game IDs from a JSON file. A sample file is provided in the assignment repository with the following content:

{
  "game-ids": [
    3498,
    3328,
    4200,
    5286
  ]
}

For each ID, request the game details from GET https://api.rawg.io/api/games/{id}. The application must produce a JSON file containing each game's ID, name, Metacritic score, and platform names, as shown in the following example:

{
  "games": [
    {
      "id": 3498,
      "name": "Grand Theft Auto V",
      "score": 92,
      "platforms": [
        "PlayStation 5",
        "Xbox Series S/X",
        "PlayStation 3",
        "PC",
        "PlayStation 4",
        "Xbox 360",
        "Xbox One"
      ]
    },
    {
      "id": 3328,
      "name": "The Witcher 3: Wild Hunt",
      "score": 92,
      "platforms": [
        "PlayStation 5",
        "Xbox Series S/X",
        "macOS",
        "PlayStation 4",
        "Nintendo Switch",
        "PC",
        "Xbox One"
      ]
    },
    {
      "id": 4200,
      "name": "Portal 2",
      "score": 95,
      "platforms": [
        "PlayStation 3",
        "PC",
        "Xbox 360",
        "Linux",
        "macOS",
        "Xbox One"
      ]
    },
    {
      "id": 5286,
      "name": "Tomb Raider",
      "score": 86,
      "platforms": [
        "PlayStation 3",
        "Xbox 360",
        "macOS",
        "PC"
      ]
    }
  ]
}

Implement two versions of the application:

  1. Using Promises explicitly
  2. Using the async/await style

REMARK: Students must handle request and file-system errors and consider the RAWG API request limits.

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