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Oct 4, 2019 · Scope is determining where variables, functions, and objects are accessible in your code during run-time. Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope before code execution. Closure gives you access to an outer function's scope from an inner function. Question 1.
Sep 30, 2023 · Today we will explore the most fundamental concepts of Javascript such as Hoisting, Scopes, and Closures. But before we tackle these concepts, we must understand how JavaScript code actually...
Oct 23, 2018 · It may seem surprising, but in my opinion the most important and fundamental concept to understanding the JavaScript language is understanding Execution Context. By properly learning it, you'll be positioned nicely to learn more advanced topics like hoisting, scope chains, and closures.
Oct 9, 2024 · Hoisting is the default behavior in JavaScript where variable and function declarations are moved to the top of their respective scopes during the compilation phase. This guarantees that regardless of where these declarations appear within a scope, they can be accessed throughout that scope.
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- Lexical scoping. Consider the following example code: js function init() { var name = "Mozilla"; // name is a local variable created by init function displayName() { // displayName() is the inner function, that forms the closure console.log(name); // use variable declared in the parent function } displayName(); } init();
- Closure. Consider the following code example: js function makeFunc() { const name = "Mozilla"; function displayName() { console.log(name); } return displayName; } const myFunc = makeFunc(); myFunc();
- Practical closures. Closures are useful because they let you associate data (the lexical environment) with a function that operates on that data. This has obvious parallels to object-oriented programming, where objects allow you to associate data (the object's properties) with one or more methods.
- Emulating private methods with closures. Languages such as Java allow you to declare methods as private, meaning that they can be called only by other methods in the same class.
Hoisting is JavaScript's default behavior of moving all declarations to the top of the current scope (to the top of the current script or the current function). The let and const Keywords Variables defined with let and const are hoisted to the top of the block, but not initialized .
Feb 1, 2022 · In this article, we’ll learn about scope and closures, which enable this behavior. Introducing Scope in JavaScript. Scope is the first piece that will help us understand the previous example. A variable’s scope is the part of a program where it is available for use.
