What is the Default Access Modifier for Variables in JavaScript?

What is the default access modifier for variables when public, private, or protected keywords are not used in JavaScript?

In JavaScript, when variables are declared without explicit access modifiers like public, private, or protected, their accessibility and scope are determined by the context in which they are declared. Here’s a detailed explanation:

// Global Scope Example
var globalVar = 'I am global';

function exampleFunction() {
    var localVar = 'I am local';
    console.log(globalVar); // Accessible
    console.log(localVar); // Accessible
}

exampleFunction();
console.log(globalVar); // Accessible
console.log(localVar); // ReferenceError: localVar is not defined

Causes

• Variables declared using `var`, `let`, or `const` outside of any function or block are accessible globally (public).
• Variables declared inside a function or a block (e.g., within curly braces of an if statement) are scoped to that function or block (local scope).

Solutions

• To restrict access to a variable, consider using closures, modules, or classes with private properties (e.g., using the `#` syntax in modern JavaScript).
• Use IIFE (Immediately Invoked Function Expressions) to create a local scope for variables within a function.

Mistake: Assuming variables declared within a function are globally accessible.

Solution: Remember that variables declared within a function have local scope and are not accessible outside of that function.

Mistake: Using the wrong declaration keyword (e.g., using `var` when `let` or `const` may be more appropriate).

Solution: Use `let` or `const` for block-scoped variables to ensure they are limited to the nearest enclosing block.