Basic Knowledge

• 数据类型
  • number
    • isInteger
  • string
    • .length
  • boolean
  • object
    • Object.freeze()
    • get
    • set
    • construct
  • array
    • filter(item, index, array)
    • map
    • spread operator: ... return comma seperated array
  • symbol
  • undefined
  • null
• 未声明的变量使用时自动在全局定义
• ===, !==
• let : 不能多次声明
  • When you declare a variable with the let keyword inside a block, statement, or expression, its scope is limited to that block, statement, or expression
• "use strict"; : 必须声明
• const : read-only
  • objects (including arrays and functions) assigned to a variable using const are still mutable
• Anonymous Functions: arrow function syntax
  • function() {}
  • () => {}
  • () => "value"
• require
• import