Block Scope. Before ES6 (2015), JavaScript variables had only Global Scope and Function Scope. ES6 introduced two important new JavaScript keywords: let and const. These two keywords provide Block Scope in JavaScript. Variables declared inside a { } block cannot be accessed from outside the block:

Block Scope. Before ES6 (2015), JavaScript did not have Block Scope. JavaScript had Global Scope and Function Scope. ES6 introduced the two new JavaScript keywords: let and const. These two keywords provided Block Scope in JavaScript:

Block Scope. A block of code refers to all of the code between curly braces {}. Variables declared inside blocks of code are only accessible by the code between the curly braces, which follows the line in which the variable was declared:

The scope is the binding part between the HTML (view) and the JavaScript (controller). The scope is an object with the available properties and methods. The scope is available for both the view and the controller.

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 .

A closure is a function that has access to the parent scope, after the parent function has closed. Closures has historically been used to: Create private variables; Preserve state between function calls; Simulate block-scoping before let and const existed; Implement certain design patterns like currying and memoization

JavaScript Function Syntax. A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses (). Function names can contain letters, digits, underscores, and dollar signs (same rules as variables). The parentheses may include parameter names separated by commas: (parameter1, parameter2, ...)

Local Scope. A variable created inside a function belongs to the local scope of that function, and can only be used inside that function.

The CSS @scope rule allows you to select elements in specific DOM subtrees. With this at-rule you can target elements precisely without writing overly-specific selectors. This at-rule also reduces coupling between your selectors and the DOM structure.

The typeof operator in JavaScript returns "function" for functions. But, JavaScript functions can best be described as objects. JavaScript functions have both properties and methods .