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Introduction

Alongside HTML and CSS, JavaScript is one of the core technologies of the World Wide Web.

Initially only implemented client-side in web browsers, JavaScript engines are now embedded in many other types of host software, including server-side in web servers and databases, and in non-web programs such as word processors and PDF software, and in runtime environments that make JavaScript available for writing mobile and desktop applications, including desktop widgets.

Fundamental Key Ideas

  • Load and go Deliver
  • Loose Typing (no specific data type)
  • Objects as general containers (Can add/update anything to object)
  • Prototypal Inheritance (can inherit from other object without use of class)
  • Lambda

A Survery of Langauage

Mostly taken form A Survey of the Language: Part One of Javascript: The Good Parts Master Class with Douglas Crockford

https://player.oreilly.com/videos/9780596809621

Values

  • Numbers
  • Strings
  • Booleans
  • Objects
  • null
  • undefined

Number

  • Only just one number type for interger/float/double
  • A point to consider that 0.1 + 0.2 !== 0.3
  • Special number = Not a Number (NaN)
    • result of undefined or erroneous operations
    • NaN is not equal to anything even itself i.e. (NaN === NaN) will be false
  • Number (value) Converts to value
  • parseInt (value, 10). Stops at first non digit character
    • parseInt("08se") === 08
  • Methods
    • abs,floor,log,max,pow,random,round,sin,sqrt

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number

String

  • Sequence of 0 or more 16-bit
  • Strings are immutable
  • String single/double quote
  • Have properties like String.length
  • Can convert to string using `String(value)``
  • Operations available: charAt, concat, indexOf, lastIndexOf, match, replace, search, slice, split, substring, toLowerCase, toUpperCase

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String

null

  • a value that has nothing in it

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/null

undefined

  • A value that isn't even that
  • the default value for variables and parameters
  • the value of missing members in Objects

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined

Booleans

  • true/false
  • To convert to boolean you can use Boolean() or !!

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean

falsy values

  • false
  • null
  • undefined
  • ""
  • 0
  • NaN

All other are truthy

  • "0", "false"

Object

Everything else in an Object

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object