The main difference between var, let, and const in ES6 is their scope and immutability. var is function-scoped and mutable, let is block-scoped and mutable, while const is block-scoped and immutable once assigned a value. const variables cannot be reassigned, but their properties can be modified if they are objects.
Arrow functions in ES6 are a more concise way to write functions in JavaScript. They use a shorter syntax and do not bind their own `this` value. For example: ``` const add = (a, b) => a + b; console.log(add(2, 3)); // Output: 5 ```
ES6 template literals offer a more concise and legible way to concatenate strings compared to traditional string concatenation. With template literals, you can embed expressions within backticks and use placeholders (${...}) to insert variables or expressions directly into the string without needing to use the '+' operator.
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ExploreES6 introduced several new features for handling asynchronous operations, including Promises for more readable and manageable asynchronous code, the async/await keywords for writing synchronous-looking code that executes asynchronously, and the arrow functions for concise syntax in callback functions.
Destructuring assignment is a feature in ES6 that allows you to extract values from arrays or objects and assign them to variables in a more concise and readable way. It simplifies the process of extracting multiple values at once without having to access them individually.
ES6 classes are a way to create objects in JavaScript using a more "classical" object-oriented syntax. Classes provide a more organized and familiar structure for defining objects compared to traditional constructor functions, making the code more readable and understandable.
The spread operator (...) in ES6 allows for expanding an iterable (like an array) into individual elements. It can be used in function arguments, array literals, and more to make code cleaner and easier to work with. This feature simplifies tasks like copying arrays, merging objects, and more.
Modules in ES6 allow developers to separate their code into different files, making it more organized and reusable. Modules offer better control over the scope of variables and functions, preventing naming conflicts. This differs from the script tag approach, which entails including all code in a single script tag.
ES6 Promises provide improved handling of asynchronous operations by allowing better control over callbacks and error handling. They feature methods like .then() and .catch() for chaining asynchronous operations and handling errors. Promises have a more organized and readable syntax compared to traditional callback functions in JavaScript.
You can ensure that a function only accepts a certain type of argument in ES6 by using the built-in feature called "default parameters." By setting the default parameter to a specific type, the function will only accept arguments that match that type.
Rest parameters in ES6 allow functions to accept an indefinite number of arguments as an array. They are denoted with three dots (...) before the last named parameter in a function declaration. This enables handling multiple arguments in a flexible and concise manner within a function.
The 'let' keyword is used to declare block-scoped variables in ES6, meaning they are only accessible within the block they are defined in. The 'const' keyword declares variables with constant values that cannot be reassigned. Both 'let' and 'const' provide better scope control and prevent unintended variable mutations.
Generators in ES6 are special types of functions that can pause execution and yield multiple values over time with the use of the `yield` keyword. They differ from normal functions in that they can be paused and resumed, allowing for efficient handling of asynchronous tasks and iteration protocols.
Symbols are a new primitive data type introduced in ES6. They are unique and immutable values that can be used as object property keys, ensuring their uniqueness. Symbols help prevent naming collisions in object properties and allow for the creation of private object members.
To export functions and variables in ES6 modules, you can use the `export` keyword before the variable or function declaration. For example, `export function myFunction() {}` or `export const myVariable = 42`. To import these exports into another module, you use the `import` keyword followed by the variable or function name.
Some of the new array methods introduced in ES6 are `map()`, `filter()`, `reduce()`, `find()`, `findIndex()`, and `forEach()`. These methods simplify array manipulation by providing a more concise and readable way to perform common operations like transforming elements, filtering items, reducing arrays, and searching for specific elements.
Async/await is a feature in ES6 that simplifies asynchronous code handling. It allows developers to write asynchronous code in a synchronous manner, making it easier to read and understand. This feature is built on top of Promises and helps to avoid callback hell by using a more linear code structure.
Higher-order functions in ES6 are functions that can take other functions as parameters or return functions as results. They are useful in functional programming because they enable more flexible and modular code structure, allowing for operations to be parameterized and easily reused across different parts of an application.
ES6 default parameters allow you to define default values for function parameters in case the arguments are not provided when the function is called. This simplifies function declarations by reducing the need for manual checking of undefined values and providing fallback values automatically.
In ES6, classes allow us to create blueprints for objects using a more familiar syntax. Inheritance in ES6 enables a class to inherit properties and methods from another class. For example, consider a `Vehicle` class with properties like `make` and `model`, and a `Car` class that extends `Vehicle` inheriting those properties.
The main difference between var, let, and const in ES6 is their scope and immutability. var is function-scoped and mutable, let is block-scoped and mutable, while const is block-scoped and immutable once assigned a value. const variables cannot be reassigned, but their properties can be modified if they are objects.
In ES6, the main difference between var, let, and const lies in their scoping and reassignability.
- Variables declared with var are function-scoped or globally scoped. They are hoisted to the top of their function or global scope.
- They can be redeclared and updated within their scope.
Example:
function myFunction() {
if (true) {
var localVar = 'I am a local variable';
}
console.log(localVar); // I am a local variable
}
myFunction();
- Variables declared with let have block scope, meaning they are only accessible within the block in which they are defined.
- They cannot be redeclared within the same block scope but can be reassigned.
Example:
function myFunction() {
if (true) {
let localVar = 'I am a local variable';
localVar = 'Modified value';
}
console.log(localVar); // Uncaught ReferenceError: localVar is not defined
}
myFunction();
- Variables declared with const are also block-scoped and cannot be reassigned. They must be initialized with a value and that value cannot change through reassignment.
- However, for objects and arrays declared with const, their properties can be modified but the variable reference cannot be changed.
Example:
const myConstant = 10;
myConstant = 20; // Uncaught TypeError: Assignment to constant variable.
const myArray = [1, 2, 3];
myArray.push(4);
console.log(myArray); // [1, 2, 3, 4]
In summary, var is function-scoped and can be redeclared and updated, let is block-scoped and can be reassigned, while const is block-scoped, cannot be reassigned, but allows modification of object and array properties within the variable.