应用数组迭代和数组操作技术的练习.zip

 # LAB | JS Functions & Arrays <details> <summary> <h2>Learning Goals</h2> </summary> This exercise allows you to practice and apply the concepts and techniques taught in class. Upon completion of this exercise, you will be able to: - Run predefined tests in Jasmine to verify that the program meets the technical requirements. - Identify expected code behavior by reading and understanding test results and errors. - Declare and invoke functions using function declaration, function expression, and arrow function syntax. - Use the `return` keyword to return a value from a function. - Pass primitive values as arguments to functions. - Pass arrays to functions as arguments. - Access items stored in arrays using the indexes, - Add, remove and check for items in an array using the index and array methods (`unshift`, `push`, `splice`, `shift`, `pop`, `indexOf`, and `includes`). - Iterate over arrays using the `for` and `forEach` loops. <br> <hr> </details> ## Introduction Array manipulation is a common task in programming. Whether you are calculating a total for a shopping cart, grabbing only the first names from a list of people, or moving a piece on a chessboard, you are probably modifying or manipulating an array somewhere in the code. <br> ## Requirements - Fork this repo - Clone it to your machine ## Submission - Upon completion, run the following commands: ```bash git add . git commit -m "Solved lab" git push origin master ``` - Create a Pull Request so that your TAs can check your work. ## Automated Testing Introduction ### What is automated testing? Automated software testing is the process of programmatically executing an application to validate and verify that it meets the business needs, as well as the technical requirements, and that it behaves as expected. Testing should be viewed as a continuous process, not a discrete operation or single activity in the development lifecycle. Designing tests at the beginning of the product lifecycle can mitigate common issues that arise when developing complex code bases. Having a strong *test suite* can provide you the ease of mind since you will be able to confidently improve upon your work while knowing that your not breaking a previously developed feature. <br> ### Testing labs This LAB and some labs you will work on during the bootcamp are equipped with unit tests to provide automated feedback on your lab progress. <br> ### Testing with Jasmine Jasmine is an automated testing framework for JavaScript. It is designed to be used in Behavior-driven Development (**BDD**) programming, focusing more on the business value than the technical details. We have already included Jasmine in the project you just forked, so let's see how to use it to implement our code. <br> ### Usage Before starting coding, we will explain the project structure we have provided you: ``` lab-js-functions-and-arrays ├── README.md ├── SpecRunner.html ├── jasmine │ └── ... ├── src │ └── functions-and-arrays.js └── tests └── functions-and-arrays.spec.js ``` We will be working with the `src/functions-and-arrays.js`. You can find all the files in the `jasmine` folder needed to use Jasmine. All these files are already linked with the `SpecRunner.html` file. If you want to check the tests, they are in the `tests/functions-and-arrays.spec.js` file. #### Run tests Running automated tests with Jasmine is super easy. All you need to do is open the `SpecRunner.html` file in your browser. You will find something similar to this: [](https://user-images.githubusercontent.com/23629340/33389609-c2f3965c-d533-11e7-9a03-e0a89314dd98.png) #### Pass the tests You should write your code on the `src/functions-and-arrays.js` file. While following the instructions for each iteration, you should check every test and ensure it's *passing*, before moving on. Do not rush. You should take your time to read every iteration carefully and address the *breaking* tests as you progress through the exercise. When coding with tests, it is super important that you carefully read and understand the errors you are getting. This way, you will know what's expected from your code. To see the output of your JavaScript code, open the [Console in the Developer Tools](https://developer.chrome.com/docs/devtools/open/#console). **Important:** Note that **you don't need to execute the functions yourself**; the tests will automatically load and execute the functions on each test run. All you need to do is declare the functions, ensure they handle the parameters passed and return what is indicated in the iteration instructions and the test description. We provide you with a sample array for some iterations, so you can do some **manual** testing if you wish. ## Instructions While following the instructions for each iteration, carefully read the instructions and test descriptions to understand the task requirements fully. Do not rush. It would be best if you took your time to read every iteration carefully. <br> ### Iteration #1: Find the maximum Implement the function `maxOfTwoNumbers` that takes two numbers as arguments and returns the bigger number. <br> ### Iteration #2: Find the longest word Implement the function `findLongestWord` that takes as an argument an array of words and returns the longest one. If there are 2 with the same length, it should return the first occurrence. You can use the following array to test your solution: ```javascript const words = ['mystery', 'brother', 'aviator', 'crocodile', 'pearl', 'orchard', 'crackpot']; ``` <br> ### Iteration #3: Calculate the sum #### Iteration #3.1: Sum numbers Calculating a sum can be as simple as iterating over an array and adding each of the elements together. Implement the function named `sumNumbers` that takes an array of numbers as an argument and returns the sum of all the numbers in the array. Later in the course, we will learn how to do this using the `reduce` array method, making your work significantly easier. For now, let's practice _the "declarative"_ way of adding values using loops. You can use the following array to test your solution: ```javascript const numbers = [6, 12, 1, 18, 13, 16, 2, 1, 8, 10]; ``` <br> #### Bonus - Iteration #3.2: A generic `sum()` function In iteration 3, you created a function that returns the sum of an array of numbers. But what if we want to calculate the sum of the length of words in an array? What if it also includes _boolean_ values? To achieve this, we must create a function allowing this flexibility. You should implement the function `sum()` in this iteration. The function should take an array of mixed values - numbers, strings, and booleans. The function should add all the string lengths, numeric values, and numeric values of booleans to the total sum and return the sum. You can use the following array to test your solution: ```javascript const mixedArr = [6, 12, 'miami', 1, true, 'barca', '200', 'lisboa', 8, 10]; // should return: 57 ``` Note: Your function should only accept an array with numbers, strings, or booleans. If the array contains any other data type, such as an object, you should [throw an error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/throw). In JavaScript, the syntax for throwing an error is as follows: ```javascript throw new Error("Error message goes here"); ``` When specifying the error message, you should be specific and descriptive in explaining the error. <br> ### Iteration #4: Calculate the average Calculating an average is a prevalent task. So let's practice it a bit. **The logic behind this:** 1. Find the sum