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Programming Notes
  • Programming Notes
  • Web Development
    • The Modern JavaScript Tutorial
      • The JavaScript language
        • Chapter 1: An introduction
        • Chapter 2: JavaScript Fundamentals
        • Chapter 3: Code quality
        • Chapter 4: Objects: the basics
        • Chapter 5: Data types
        • Chapter 6: Advanced working with functions
        • Chapter 7: Object properties configuration
        • Chapter 8: Prototypes, inheritance
        • Chapter 9: Classes
        • Chapter 10: Error handling
        • Chapter 11: Introduction: callbacks
        • Chapter 12: Generators, advanced iteration
        • Chapter 13: Modules
        • Chapter 14: Miscellaneous
      • Browser Document, Events, Interfaces
        • Chapter 1: Document
        • Chapter 2: Introduction to Events
        • Chapter 3 UI Events
        • Chapter 4: Forms, controls
        • Chapter 5: Document and resource loading
        • Chapter 6: Miscellaneous
      • Additional articles
        • Chapter 1: Frames and windows
        • Chapter 2: Binary data, files
        • Chapter 3: Network requests
        • Chapter 4: Storing data in the browser
        • Chapter 6: Web components
    • You Don't Know JS
      • Get Started
        • Chapter 1: What Is JavaScript?
        • Chapter 2: Surveying JS
        • Chapter 3: Digging to the Roots of JS
        • Chapter 4: The Bigger Picture
        • Appendix A: Exploring Further
      • Scope and Closures
        • Chapter 1: What's the Scope?
        • Chapter 2: Illustrating Lexical Scope
        • Chapter 3: The Scope Chain
        • Chapter 4: Around the Global Scope
        • Chapter 5: The (Not So) Secret Lifecycle of Variables
        • Chapter 6: Limiting Scope Exposure
        • Chapter 7: Using Closures
        • Chapter 8: The Module Pattern
    • TypeScript Handbook
      • Basic Types
      • Functions
      • Enums
      • Interfaces
      • Unions and Intersection Types
      • Literal Types
      • Generics
    • React Internals
      • React Hooks
      • Reconciliation
      • Context
      • JSX In Depth
      • Fragments
      • Type Checking With PropTypes
      • Strict Mode
    • Vue Internals
      • Virtual DOM
      • Reactivity in Depth (Vue 2)
      • Vue Interview
    • Testing
      • An Overview of JavaScript Testing in 2020
    • Build Tools
      • Web Development: A Primer
      • Webpack 5 Documentation
  • Computer Science
    • Computer Systems
      • Bits, Bytes, and Integers
      • Machine Level Programming
      • Optimizing Program Performance
      • The Memory Hierarchy
      • Linking
      • Exceptional Control Flow
      • Virtual Memory
      • Concurrent Programming
    • Algorithm Design
      • Stable Matching
      • Basics of Algorithm Analysis
      • Graphs
      • Greedy Algorithms
      • Divide and Conquer
      • Dynamic Programming
      • NP and Computational Intractability
      • Randomized Algorithms
    • Data Structures
      • Intro, Hello World Java
      • Defining and Using Classes
      • References, Recursion, and Lists
      • SLLists, Nested Classes, Sentinel Nodes
      • DLLists, Arrays
      • ALists, Resizing, vs. SLists
      • Testing
      • Inheritance, Implements
      • Extends, Casting, Higher Order Functions
      • Subtype Polymorphism vs. HoFs
      • Exceptions, Iterators, Object Methods
      • Asymptotics I
      • Disjoint Sets
      • Asymptotics II
      • ADTs, Sets, Maps, BSTs
      • B-Trees (2-3, 2-3-4 Trees)
      • Red Black Trees
      • Hashing
      • Heaps and PQs
      • Prefix Operations and Tries
      • Range Searching and Multi-Dimensional Data
      • Tree and Graph Traversals
      • Graph Traversals and Implementations
      • Shortest Paths
      • Minimum Spanning Trees
      • Reductions and Decomposition
      • Basic Sorts
      • Quick Sort
      • More Quick Sort, Sorting Summary
      • Sorting and Algorithmic Bounds
      • Radix Sorts
      • Sorting and Data Structures Conclusion
      • Compression
      • Compression, Complexity, and P=NP?
  • Software Engineering
    • Refactoring
      • Code Smells
        • Other Smells
        • Couplers
        • Object-Orientation Abusers
        • Change Preventers
        • Dispensables
        • Bloaters
      • Refactoring Techniques
        • Composing Methods
    • System Design
      • AWS Certified Solutions Architect - 2019
        • Basic Concepts
        • Applications
        • Databases
        • EC2
        • IAM
        • Lambda
        • Route53
        • S3
        • VPC
Powered by GitBook
On this page
  • 1.1 An Introduction to JavaScript
  • What is JavaScript?
  • How do engines work?
  • What can in-browser JavaScript do?
  • What Can't in-browser JavaScript do?
  • What makes JavaScript unique?
  • Languages "over" JavaScript
  • 1.2 Manuals and specifications
  • Specification
  • Manuals
  • 1.3 Code editors
  • IDE
  • 1.4 Developer console
  1. Web Development
  2. The Modern JavaScript Tutorial
  3. The JavaScript language

Chapter 1: An introduction

1.1 An Introduction to JavaScript

What is JavaScript?

JavaScript was initially created to "make web pages alive". They can be written right in a web page's HTML and run automatically as the page loads. The browser has an embedded engine sometimes called a "JavaScript virtual machine". (V8, SpiderMondy, ChakraCore, etc.)

How do engines work?

  1. The engine (embedded if it's a browser) reads ("parses") the script.

  2. Then it converts ("compiles") the script to the machine language.

  3. And then the machine code runs, pretty fast. (The engine applies optimizations at each step of the process.)

What can in-browser JavaScript do?

JavaScript does not provide low-level access to memory or CPU. JavaScript's capabilities greatly depend on the environment it's running in. (Node.js supports reading and writing arbitrary files, performing network requests, etc.)

In-browser JavaScript can do everything related to webpage manipulation, interaction with the user, and the webserver. (Add or change the HTML, react to user actions, send requests over the network, get and set cookies, save data into the local storage, etc.)

What Can't in-browser JavaScript do?

JavaScript's abilities in the browser are limited for the sake of the user's safety to prevent evil webpages from harming the user's privacy and data.

  • Read or write files on the disk, or execute programs.

  • Different tabs/windows generally do not know about each other if they come from different sites. (Same Origin Policy)

  • Its ability to receive data from other sites/domains is crippled.

What makes JavaScript unique?

  • Full integration with HTML/CSS.

  • Simple things are done simply.

  • Support by all major browsers and enabled by default.

  • Allows to create servers, mobile applications, etc.

Languages "over" JavaScript

A plethora of new languages appeared, which are transpiled (converted) to JavaScript before they run in the browser.

  • CoffeeScript: a "syntactic sugar" for JavaScript

  • TypeScript: strict data typing

  • Flow: data typing

  • Dart: has its own engine that runs in non-browser environments

1.2 Manuals and specifications

Specification

The ECMA-262 specification contains the most in-depth, detailed and formalized information about JavaScript. It defines the language.

To read about new bleeding-edge features: https://github.com/tc39/proposals

Manuals

  • MDN (Mozilla) JavaScript Reference

  • MSDN Compatibility tables

  • http://caniuse.com: per-feature tables of support

  • https://kangax.github.io/compat-table: a table with language features and engines that support those or don't support.

1.3 Code editors

IDE

  • Visual Studio Code

  • WebStorm Lightweight editors

  • Atom

  • Sublime Text

  • Notepad++

  • Vim or Emacs

1.4 Developer console

Developer tools allow us to see errors, run commands, examine variables, and much more.

They can be opened with F12 for most browsers on Windows. Chrome for Mac needs Cmd+Opt+J, Safari: Cmd+Opt+C (need to enable first).

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Last updated 4 years ago