JavaScript is a popular programming language used for web development. Among its many features are advanced concepts that make it a versatile language. In this article, we will explore these concepts, including array methods, closures, classes, promises, and generators.<\/p>\n
JavaScript arrays are versatile data structures that can hold any type of data, including other arrays and objects. They also offer several built-in methods for manipulating data. Here are four advanced array methods you should know:<\/p>\n
The The The The A closure is a function that has access to variables in its outer (enclosing) function’s scope chain, even after the outer function has returned.<\/p>\n In the above example, JavaScript classes are a version of JavaScript’s prototypical inheritance. They provide a way to define complex objects with their own methods and properties, much like traditional object-oriented programming (OOP) languages.<\/p>\n In the above example, we define a We can also extend existing classes to create new classes with added functionality.<\/p>\n In the above example, we define a Promises are objects that represent the eventual completion (or failure) of an asynchronous operation and its resulting value. They provide an alternative to working with callbacks.<\/p>\n In the above example, we define a In the above example, we use the Generators are functions that can be paused and resumed, allowing for the creation of iterators. They offer a powerful way to write asynchronous and concurrent code in a synchronous style.<\/p>\n In the above example, we define a map<\/code> method creates a new array with the results of calling a provided function on every element in the calling array. This method does not modify the original array.<\/p>\nconst numbers = [1, 2, 3, 4];\nconst doubledNumbers = numbers.map(number => number * 2);\nconsole.log(doubledNumbers); \/\/ [2, 4, 6, 8]\n<\/code><\/pre>\nfilter<\/h3>\n
filter<\/code> method creates a new array with all elements that pass the test implemented by the provided function. This method does not modify the original array.<\/p>\nconst numbers = [1, 2, 3, 4];\nconst evenNumbers = numbers.filter(number => number % 2 === 0);\nconsole.log(evenNumbers); \/\/ [2, 4]\n<\/code><\/pre>\nreduce<\/h3>\n
reduce<\/code> method applies a function against an accumulator and each element in the array to reduce it to a single value. This method does not modify the original array.<\/p>\nconst numbers = [1, 2, 3, 4];\nconst sum = numbers.reduce((accumulator, currentValue) => accumulator + currentValue);\nconsole.log(sum); \/\/ 10\n<\/code><\/pre>\nforEach<\/h3>\n
forEach<\/code> method executes a provided function once for each array element. This method does not create a new array and does not modify the original array.<\/p>\nconst numbers = [1, 2, 3, 4];\nnumbers.forEach(number => console.log(number * 2)); \/\/ 2, 4, 6, 8\n<\/code><\/pre>\nClosures<\/h2>\n
const outerFunction = () => {\n const outerVariable = 'outer variable';\n\n const innerFunction = () => {\n console.log(outerVariable);\n };\n\n return innerFunction;\n};\n\nconst innerFunction = outerFunction();\ninnerFunction(); \/\/ 'outer variable'\n<\/code><\/pre>\ninnerFunction<\/code> has access to the outerVariable<\/code>, even though it is not directly declared inside the innerFunction<\/code>.<\/p>\nClasses<\/h2>\n
Defining classes<\/h3>\n
class Dog {\n constructor(name, breed) {\n this.name = name;\n this.breed = breed;\n }\n\n bark() {\n console.log('Woof!');\n }\n\n displayInfo() {\n console.log(`Name: ${this.name}, Breed: ${this.breed}`);\n }\n}\n\nconst myDog = new Dog('Rufus', 'Labrador');\nmyDog.displayInfo();\nmyDog.bark();\n<\/code><\/pre>\nDog<\/code> class with a constructor function that takes a name<\/code> and breed<\/code> argument and sets them as properties of the new instance. We also define a bark<\/code> method and a displayInfo<\/code> method that logs information about the dog instance.<\/p>\nExtending classes<\/h3>\n
class ServiceDog extends Dog {\n constructor(name, breed, serviceType) {\n super(name, breed);\n this.serviceType = serviceType;\n }\n\n performService() {\n console.log(`Performing ${this.serviceType} service.`);\n }\n}\n\nconst myServiceDog = new ServiceDog('Lacey', 'Golden Retriever', 'Therapy');\nmyServiceDog.displayInfo();\nmyServiceDog.bark();\nmyServiceDog.performService();\n<\/code><\/pre>\nServiceDog<\/code> class that extends the Dog<\/code> class. We use the super()<\/code> method to call the Dog<\/code> class constructor and add a serviceType<\/code> property. We also define a performService<\/code> method that is specific to the ServiceDog<\/code> class.<\/p>\nPromises<\/h2>\n
Creating promises<\/h3>\n
const myPromise = new Promise((resolve, reject) => {\n setTimeout(() => {\n resolve('Success!');\n }, 1000);\n});\n<\/code><\/pre>\nmyPromise<\/code> object with a constructor function that takes a resolve<\/code> and reject<\/code> argument. We use the setTimeout()<\/code> function to simulate an asynchronous operation that resolves after one second and returns the string 'Success!'<\/code>.<\/p>\nWorking with promises<\/h3>\n
myPromise\n .then(result => console.log(result))\n .catch(error => console.log(error));\n<\/code><\/pre>\n.then()<\/code> method to handle the resolved myPromise<\/code> result and the .catch()<\/code> method to handle any errors. This results in the string 'Success!'<\/code> being logged to the console after one second.<\/p>\nGenerators<\/h2>\n
Defining generators<\/h3>\n
function* myGenerator() {\n yield 1;\n yield 2;\n yield 3;\n}\n\nconst generator = myGenerator();\n\nconsole.log(generator.next().value); \/\/ 1\nconsole.log(generator.next().value); \/\/ 2\nconsole.log(generator.next().value); \/\/ 3\n<\/code><\/pre>\nmyGenerator<\/code> function that uses the yield<\/code> keyword to define a set of values to be returned by the generator. We create an instance of the generator and use the .next()<\/code> method to iterate through the values.<\/p>\nSending data to generators<\/h3>\n
function* myGenerator() {\n const greeting = yield;\n console.log(greeting);\n}\n\nconst generator = myGenerator();\n\ngenerator.next();\ngenerator.next('Hello!'); \/\/ 'Hello!'\n<\/code><\/pre>\n