String()和toString()的区别和应用

应用

let a = 1
let b= 123

String(a) // '1'
typeOf a // String

b.toString() // '123'
typeOf b // String

区别

• toString()无法转换nudefined、null

let a
let b = null
a.toString() // Uncaught TypeError: Cannot read property 'toString' of undefined
b.toString() // Uncaught TypeError: Cannot read property 'toString' of undefined

String(a) // 'undefined'
String(b) // 'null'