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참고

• 원문 ECMAScript 6 — New Features: Overview & Comparison
• 번역1
• 번역2
• 번역3

1. const

   • Constants

    const PI = 3.141593
   

   • let과 const 는 중괄호(“{}”)로 정의된 블록으로 유효 범위(스코프)를 지정하는 새로운 var 이다
   • var 는 전역 또는 함수 내부로 유효 범위를 갖는다
   • var 호이스팅(hoisting)
     • 변수 선언이 함수 또는 전역 코드의 상단에 이동하는 것과 같은 행동을 “호이스팅(hoisting)”이라고 불립니다.

2. scope

   • Block-Scoped Variables
     • Block-scoped variables (and constants) without hoisting.
   • Block-Scoped Functions
     • Block-scoped function definitions.

3. arrow function

   • Expression Bodies
     • More expressive closure syntax

         map(v => v + 1)
       

   • Statement Bodies
     • More expressive closure syntax
   • Lexical this
     • More intuitive handling of current object context.

4. Extended Parameter Handling

   • Default Parameter Values
   • Rest Parameter
   • Spread Operator

5. Template Literals

   • String Interpolation
   • Custom Interpolation
   • Raw String Access

6. Extended Literals

   • Binary & Octal Literal
   • Unicode String & RegExp Literal

7. Enhanced Regular Expression

   • Regular Expression Sticky Matching

8. Enhanced Object Properties

   • Property Shorthand
   • Computed Property Names
   • Method Properties

9. Destructuring Assignment

   • Array Matching
   • Object Matching, Shorthand Notation
   • Object Matching, Deep Matching
   • Object And Array Matching, Default Values
   • Parameter Context Matching
   • Fail-Soft Destructuring

10. Modules

    • Value Export/Import
    • Default & Wildcard

11. Classes

    • Class Definition
      • More intuitive, OOP-style and boilerplate-free classes.
    • Class Inheritance
      • More intuitive, OOP-style and boilerplate-free inheritance.
    • Class Inheritance, From Expressions
    • Base Class Access

        super.xxx
      

    • Static Members
    • Getter/Setter
12. Symbol Type
    • Symbol Type

        Symbol('foo') !== Symbol('foo')
        const foo = Symbol()
        const bar = Symbol()
        typeof foo === 'symbol'
        typeof bar === 'symbol'
        let obj = {}
        obj[foo] = 'foo'
        obj[bar] = 'bar'
        JSON.stringify(obj) // {}
        Object.keys(obj) // []
        Object.getOwnPropertyNames(obj) // []
        Object.getOwnPropertySymbols(obj) // [ foo, bar ]
      

    • Global Symbols

        Symbol.for('app.foo') === Symbol.for('app.foo')
      

13. Iterators

    • Iterator & For-Of Operator

14. Generators

    yield
    

15. Map/Set & WeakMap/WeakSet

    • Set Data-Structure

    let s = new Set()
    s.add('hello').add('goodbye').add('hello')
    s.size === 2
    s.has('hello') === true
    for (let key of s.values()) // insertion order
        console.log(key)
    

    • Map Data-Structure

    let m = new Map()
    let s = Symbol()
    m.set('hello', 42)
    m.set(s, 34)
    m.get(s) === 34
    m.size === 2
    for (let [key, val] of m.entries()) console.log(key + ' = ' + val)
    

    • Weak-Link Data-Structures
      • Memory-leak-free Object-key’d side-by-side data-structures.

16. Typed Arrays

    • Typed Arrays

17. New Built-In Methods

    • Object Property Assignment

    Object.assign(dest, src1, src2)
    

    • Array Element Finding

    ;[1, 3, 4, 2]
        .find(x => x > 3) // 4
        [(1, 3, 4, 2)].findIndex(x => x > 3) // 2
    

    • String Repeating

    'foo'.repeat(3)
    

    • String Searching

    'hello'.startsWith('ello', 1) // true
    'hello'.endsWith('hell', 4) // true
    'hello'.includes('ell') // true
    'hello'.includes('ell', 1) // true
    'hello'.includes('ell', 2) // false
    

    • Number Type Checking

    Number.isNaN()
    Number.isFinite()
    

    • Number Safety Checking

    Number.isSafeInteger()
    

    • Number Comparison

    Number.EPSILON
    

    • Number Truncation

    console.log(Math.trunc(42.7)) // 42
    console.log(Math.trunc(0.1)) // 0
    console.log(Math.trunc(-0.1)) // -0
    

    • Number Sign Determination

18. Promises

    • Promise Usage
    • Promise Combination

19. Meta-Programming

    • Proxying

    let target = {
        foo: 'Welcome, foo',
    }
    let proxy = new Proxy(target, {
        get(receiver, name) {
            return name in receiver ? receiver[name] : `Hello, ${name}`
        },
    })
    proxy.foo === 'Welcome, foo'
    proxy.world === 'Hello, world'
    

    • Reflection

    let obj = {a: 1}
    Object.defineProperty(obj, 'b', {value: 2})
    obj[Symbol('c')] = 3
    Reflect.ownKeys(obj) // [ "a", "b", Symbol(c) ]
    

20. Internationalization & Localization
    • Collation
      • Sorting a set of strings and searching within a set of strings. Collation is parameterized by locale and aware of Unicode.
    • Number Formatting

      var l10nEN = new Intl.NumberFormat('en-US')
      var l10nDE = new Intl.NumberFormat('de-DE')
      l10nEN.format(1234567.89) === '1,234,567.89'
      l10nDE.format(1234567.89) === '1.234.567,89'
      

    • Currency Formatting

      var l10nUSD = new Intl.NumberFormat('en-US', {style: 'currency', currency: 'USD'})
      l10nUSD.format(100200300.4) === '$100,200,300.40'
      

    • Date/Time Formatting

      var l10nEN = new Intl.DateTimeFormat('en-US')
      l10nEN.format(new Date('2015-01-02')) === '1/2/2015'