JavaScript | typeof运算符功能

typeof运算符功能

• 识别所有值类型

  let a
  const b = true
  const n = 123
  const str = 'abc'
  const big = 2n //A BigInt is created by appending n to the end of an integer or by calling the constructor.
  const bigi = BigInt(3)
  const s = Symbol('s')
    
  console.log(`typeof a ? ${typeof a}`); // undefined
  console.log(`typeof b ? ${typeof b}`); // boolean
  console.log(`typeof n ? ${typeof n}`); // number
  console.log(`typeof str ? ${typeof str}`); // string
  console.log(`typeof big ? ${typeof big}`); // bigint
  console.log(`typeof bigi ? ${typeof bigi}`); // bigint
  console.log(`typeof s ? ${typeof s}`); //symbol
  

• 识别函数

  console.log(`typeof console.log ? ${typeof console.log}`); // function
  console.log(`typeof function () {} ? ${typeof function () {}}`); // function
  

• 判断是否是引用类型（不可再细分）

  console.log(`typeof null ? ${typeof null}`); // object
  console.log(`typeof ['a', 'b'] ? ${typeof ['a', 'b']}`); // object
  console.log(`typeof {x: 9} ? ${typeof {x: 9}}`); // object
  const map = new Map()
  console.log(`typeof map ? ${typeof map}`); // object
  

注意值类型和基本(primitive)数据类型范围不一样