Asynchronous JavaScript

2.

Legacy Asynchronous Patterns: Callbacks

2.1.

Understanding Callback Functions

2.1.1.

Definition of Callback Functions

2.1.2.

Higher-Order Functions

2.1.2.1.

Functions Accepting Other Functions

2.1.2.2.

Use Cases in Asynchronous Code

2.1.3.

Passing Functions as Arguments

2.1.3.1.

Syntax and Examples

2.1.3.2.

Anonymous vs. Named Functions

2.2.

Implementing Asynchronous Callbacks

2.2.1.

setTimeout Example

2.2.1.1.

Scheduling Delayed Execution

2.2.1.2.

Callback Function Signature

2.2.2.

Event Listeners Example

2.2.2.1.

Registering Event Handlers

2.2.2.2.

Asynchronous Event Handling

2.2.3.

Node.js Asynchronous APIs Example

2.2.3.1.

File System Callbacks

2.2.3.2.

Error-First Callback Pattern

2.3.

The Callback Hell Problem

2.3.1.

The Pyramid of Doom

2.3.1.1.

Deeply Nested Callbacks

2.3.1.2.

Readability Issues

2.3.2.

Issues with Readability and Maintainability

2.3.2.1.

Difficulty in Tracing Execution Flow

2.3.2.2.

Challenges in Error Handling

2.3.2.3.

Scalability Concerns

2.4.

Error Handling with Callbacks

2.4.1.

The Error-First Convention

2.4.1.1.

Error as the First Argument

2.4.1.2.

Handling Success and Failure

2.4.2.

Propagating Errors in Callback Chains

2.4.3.

Limitations of Callback-Based Error Handling

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1. Foundations of Asynchronous JavaScript

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3. The Promise API