Upgrading to ES8: What You Need to Know to Take Full Advantage of the Latest JavaScript Features

JavaScript has become an incredibly versatile language in recent years, and with the introduction of ECMAScript 2017 (ES8), the language has taken another leap forward. ES8 introduces several new features and improvements that can help developers write cleaner, more concise, and more powerful code. From asynchronous iteration and shared memory to trailing commas and improvements to regular expressions, ES8 has something for everyone. In this article, we'll explore all the new features of ES8, what they are, and how they can be used to improve your JavaScript development. Whether you're a seasoned pro or just starting with JavaScript, this guide will help you take full advantage of the latest and greatest features of the language.

Table of content:

1. Async Functions
2. Shared Memory and Atomics
3. Object.values() and Object.entries()
4. String padding
5. Trailing commas in function parameter lists and calls
6. Object.getOwnPropertyDescriptors()

1. Async Functions:

Async/Await syntax, which provides a clean and concise way to write asynchronous code in JavaScript.

The async/await syntax is built on top of Promises, which were introduced in ES6.

Here's an example of using async/await to make an API call and parse the response:

async function fetchUserData(userId) {
  const response = await fetch(`https://api.example.com/users/${userId}`); 
  const userData = await response.json();  
  return userData; 
}         

In this example, the fetchUserData function is declared as an async function, which allows us to use the await keyword inside it. The await keyword is used to wait for a Promise to resolve, and it can only be used inside an async function.

The fetch function returns a Promise that resolves to a Response object. We use await to wait for this Promise to resolve and store the Response object in the response variable.

Next, we call the json method on the Response object to parse the response body as JSON. Again, we use await to wait for this Promise to resolve and store the parsed JSON data in the userData variable.

Finally, we return the userData object from the fetchUserData function.

Here's another example of using async/await to perform multiple API calls in parallel:

async function fetchUserData(userId) { 
 const [userResponse, postsResponse] = await Promise.all([ fetch(`https://api.example.com/users/${userId}`), fetch(`https://api.example.com/posts?userId=${userId}`) ]); 
 const userData = await userResponse.json(); const postsData = await postsResponse.json(); return { user: userData, posts: postsData }; 
}        

In this example, we use the Promise.all method to wait for multiple Promises to resolve in parallel. The Promise.all method takes an array of Promises and returns a new Promise that resolves to an array of the resolved values of the input Promises.

We pass two Promises to Promise.all: one for fetching user data and one for fetching posts data. We use array destructuring to assign the resolved values of these Promises to the userResponse and postsResponse variables.

We then use await to wait for each of these Promises to resolve and parse the response bodies as JSON.

Finally, we return an object that contains the parsed user and posts data.

2. Shared Memory and Atomics:

Shared memory allows multiple threads to access the same memory location and communicate with each other.

Atomic operations are used to ensure that these threads can access and manipulate shared data without conflicts or race conditions.

Shared Memory:

In JavaScript, the concept of shared memory is implemented using SharedArrayBuffer and Atomics objects. SharedArrayBuffer is a special type of buffer that can be accessed by multiple threads at the same time. However, it does not provide any synchronization mechanism to avoid race conditions. To prevent race conditions, the Atomics object provides a set of atomic operations that can be used to manipulate data in the shared memory.

Here is an example code snippet that demonstrates the usage of SharedArrayBuffer and Atomics object:

const sab = new SharedArrayBuffer(4); // create a shared buffer of 4 bytes 
const arr = new Int32Array(sab); // create an array view of the buffer 
// set the value of the shared memory 
Atomics.store(arr, 0, 10); 
// get the value of the shared memory 
console.log(Atomics.load(arr, 0)); // output: 10 
// add 5 to the value of the shared memory 
Atomics.add(arr, 0, 5); 
// get the updated value of the shared memory 
console.log(Atomics.load(arr, 0)); // output: 15         

In the above example, we create a SharedArrayBuffer of 4 bytes and an Int32Array view of the buffer. We use the Atomics.store() method to set the value of the shared memory to 10. Then, we use the Atomics.load() method to get the value of the shared memory and log it to the console. After that, we use the Atomics.add() method to add 5 to the value of the shared memory and again use the Atomics.load() method to get the updated value of the shared memory and log it to the console.

Atomics:

The Atomics object provides a set of atomic operations that can be used to manipulate data in the shared memory. These operations ensure that the data is accessed and manipulated atomically, i.e., as a single, indivisible operation, without any race conditions or conflicts.

Here is a list of atomic operations provided by the Atomics object:

• Atomics.add()
• Atomics.and()
• Atomics.compareExchange()
• Atomics.exchange()
• Atomics.load()
• Atomics.or()
• Atomics.store()
• Atomics.sub()
• Atomics.wait()
• Atomics.wake()
• Atomics.xor()

Each of these methods takes an array view, an index, and one or more values as arguments, and performs the atomic operation on the data at the specified index.

Here is an example code snippet that demonstrates the usage of some of these atomic operations:

const sab = new SharedArrayBuffer(4); // create a shared buffer of 4 bytes 
const arr = new Int32Array(sab); // create an array view of the buffer 
// set the value of the shared memory 
Atomics.store(arr, 0, 10); 
// add 5 to the value of the shared memory 
Atomics.add(arr, 0, 5); 
// subtract 2 from the value of the shared memory 
Atomics.sub(arr, 0, 2); 
// bitwise OR the value of the shared memory with 0x0F 
Atomics.or(arr, 0, 0x0F); 
// bitwise AND the value of the shared memory with 0xF0
Atomics.and(arr, 0, 0xF0);
// get the updated value of the shared memory 
const value = Atomics.load(arr, 0); 
// output the value of the shared memory 
console.log(value); // output: 13 
        

In the above example, we first create a SharedArrayBuffer of 4 bytes and an Int32Array view of the buffer. We use the Atomics.store() method to set the value of the shared memory to 10. Then, we use the Atomics.add() method to add 5 to the value of the shared memory, Atomics.sub() method to subtract 2 from the value of the shared memory, Atomics.or() method to bitwise OR the value of the shared memory with 0x0F and Atomics.and() method to bitwise AND the value of the shared memory with 0xF0. Finally, we use the Atomics.load() method to get the updated value of the shared memory and log it to the console.

3. Object.values() and Object.entries():

Object.values() method which returns an array of values of an object's own enumerable properties.

Here's an example:

const obj = { a: 1, b: 2, c: 3 }; 
const values = Object.values(obj); 
console.log(values); // [1, 2, 3]         

In the code snippet above, we have an object obj with three properties, a, b, and c, each with a corresponding value. We then call the Object.values() method on this object, which returns an array of values [1, 2, 3].

Object.values() does not return the values of any inherited properties, only the values of an object's own properties.

Here's an example to illustrate this:

const parent = { a: 1 }; 
const child = Object.create(parent); 
child.b = 2; 
const childValues = Object.values(child); 
console.log(childValues); // [2]         

In the code snippet above, we have an object parent with one property a, and an object child that inherits from parent and has its own property b. We call Object.values() on child, which returns an array with the value [2]. Note that the value 1 of the inherited property a is not included in the array.

Object.keys() method, which is used to retrieve an array of all the keys in an object.

Before ES8, Object.keys() would only work with regular objects and not with objects that inherit from Object.prototype. ES8 improved this behavior by allowing Object.keys() to work with any object, including those that inherit from Object.prototype.

Here's an example of using Object.keys() in ES8:

const person = { name: 'John', age: 30 }; 
const keys = Object.keys(person); 
console.log(keys); // Output: ['name', 'age']         

In the above code snippet, we create an object person with two properties: name and age. We then use Object.keys() to retrieve an array of all the keys in the person object, which are name and age. Finally, we log the array to the console.

Here's another example:

class Car { 
  constructor(make, model) { 
    this.make = make; 
    this.model = model; 
  } 
} 
const myCar = new Car('Toyota', 'Corolla'); 
const keys = Object.keys(myCar); 
console.log(keys); // Output: ['make', 'model']         

In the above code snippet, we create a Car class with a constructor that sets the make and model properties. We then create an instance of the Car class with the new keyword and assign it to the myCar variable. We then use Object.keys() to retrieve an array of all the keys in the myCar object, which are make and model. Finally, we log the array to the console.

4. String padding:

padStart() and padEnd(). These methods allow you to pad a string with a specific character or substring to a certain length.

The padStart() method pads a string from the start (left side) with a specified character until it reaches the desired length.

The method takes two arguments: the first argument is the total length of the resulting string, and the second argument is the character to use for padding (if no character is specified, the method pads with spaces).

Here's an example of using padStart():

const str = 'hello'; 
const paddedStr = str.padStart(10, '*'); 
console.log(paddedStr); // Output: ****hello         

In the example above, the padStart() method pads the str variable with four asterisks to create a resulting string that is ten characters long.

The padEnd() method is similar to padStart(), but it pads the string from the end (right side).

Here's an example:

const str = 'hello'; 
const paddedStr = str.padEnd(10, '*'); 
console.log(paddedStr); // Output: hello****         

In this example, the padEnd() method pads the str variable with four asterisks at the end to create a resulting string that is ten characters long.

Both padStart() and padEnd() also accept a second optional argument that specifies the string to use for padding instead of a single character. Here's an example of using padEnd() with a substring:

const str = 'hello';
const paddedStr = str.padEnd(10, ' world'); 
console.log(paddedStr); // Output: hello world         

In this example, the padEnd() method pads the str variable with the string ' world' to create a resulting string that is ten characters long.

5. Trailing commas in function parameter lists and calls:

Trailing commas in function parameter lists and function calls were introduced as a new feature.

This means that a comma can now be added after the last parameter in a function's parameter list, or after the last argument in a function call, without causing a syntax error.

Trailing commas in function parameter lists can be useful when adding or removing parameters from a function. Previously, adding a new parameter to a function would require modifying the previous last parameter to include a comma after it, which could be time-consuming and error-prone. With trailing commas, adding a new parameter is as simple as appending it to the list and adding a comma after it.

Here is an example of a function with trailing commas in its parameter list:

function myFunction(param1, param2, param3,) { 
 // function body 
}         

In this example, a comma has been added after the last parameter, param3. This is a valid syntax in ES8 and will not cause an error.

Trailing commas in function calls work similarly. They allow for easier modification of the arguments list by allowing an argument to be added or removed without having to worry about whether a comma needs to be added or removed as well.

Here is an example of a function call with trailing commas:

myFunction(arg1, arg2, arg3,);         

In this example, a comma has been added after the last argument, arg3. This is also a valid syntax in ES8.

It's worth noting that trailing commas have no effect on the behavior of a function or its arguments. They are simply a convenience feature that can make code maintenance easier.

6. Object.getOwnPropertyDescriptors():

Object.getOwnPropertyDescriptors() that allows you to get all property descriptors of an object, including both own properties and inherited properties. This method returns an object with the descriptors of all the properties in the provided object.

Here's an example code snippet to illustrate the usage of Object.getOwnPropertyDescriptors():

const obj = { 
 name: 'John', 
 age: 30, 
 get fullName() { return `${this.name} Doe`; } 
}; 
const descriptors = Object.getOwnPropertyDescriptors(obj); 
console.log(descriptors.name); 
console.log(descriptors.age); 
console.log(descriptors.fullName);         

In this example, we define an object obj with three properties: name, age, and fullName. The fullName property is defined as a getter function.

We then use Object.getOwnPropertyDescriptors() to get all property descriptors of obj. The result is stored in the descriptors variable.

Finally, we log the descriptors of each property in the console. We can see that the name and age properties have descriptors with value, writable, enumerable, and configurable keys, while the fullName property has a descriptor with get, set, enumerable, and configurable keys.

// Output: 
// { value: 'John', writable: true, enumerable: true, configurable: true } 
// { value: 30, writable: true, enumerable: true, configurable: true } 
// { get: [Function: get fullName], set: undefined, enumerable: true, configurable: true }        

#javascript #es8 #asyncfunctions #SharedMemoryandAtomics #Objectvalues () #Objectentries () #Stringpadding #Trailingcommas #getOwnPropertyDescriptors ()