/ES6JavaScript-note

note for Udemy course: JavaScript: Understanding ES6 and Beyond

ES6JavaScript-note

JavaScript: Understanding ES6 and Beyond

Block Scoping

  1. lexical environment, curly brace
    • var, global
    • let, in the same block or block going up
    • const, similar to let, but the binding is immutable

Templates

  1. concatenation
    • string + string
  2. interpolation
    • replace portions of strings with other strings. It described as inserting or injecting strings into another strings
    • dollar sign and curing brace within string
    •  let firstname = Steven;
 let lastname = Jie;
 let fullname = `${firstname} ${lastname}`

Classes

  1. a structure in a programming language that provides a way to create objects
  2. class, function object
  3. instance, the actual object created from an object creation feature(like a class)
  4. how to understand __proto__ and prototype?
    • JavaScript has a built-in constructor called Object(), and the prototype property of this function points to an empty object
    • thus, we can say 
      ( new Foo ).__proto__.__proto__ === Object.prototype
      it is true
    • and 
      ( new Foo ).__proto__.__proto__.__proto__ === null
      it is true
    • if there is inheritence in it, it would be more fun, assume that Staff extends to Person, 
      let a = new Person('Rick')
let b = new Staff('Steve')
      thus, 
      b.__proto__ === Staff.prototype

Staff.prototype.__proto__ === Person.prototype 
b.__proto__.__proto__ === Person.prototype 

Person.prototype.__proto__ === Object.prototype
b.__proto__.__proto__.__proto__ === Object.prototype

Object.prototype.__proto__ === null
b.__proto__.__proto__.__proto__.__proto__ === null
      there are all true!
    • more details, refer to this link
  5. static
    • create a method or variable that it doesn't reference any of the fields in the class
  6. private fields
    • use #
    • getter, setter
  7. private methods

Arrow Functions

Iterators and Iterables

Default Parameters

  1. if parameters are undefined, then the default value will be instead of it
  2. if parameters are null, then the default value will not work