12.20---01转换字符串

1.变量.toString()

var str1 = 100
console.log(typeof(str1),str1)
console.log(typeof( str1.toString()), str1.toString())





var str1 = 100
var str2 = true
var str3 = false
var str4 = undefined
var str5 = null
console.log(typeof (str1.toString()), str1.toString())
console.log(typeof (str2.toString()), str2.toString())
console.log(typeof (str3.toString()), str3.toString())
console.log(typeof (str4.toString()), str4.toString())
console.log(typeof (str5.toString()), str5 .toString())
undefined 和null不能使用toString类型

2.String(变量)

var str1 = 100

console.log(typeof (String(str1)), String(str1))
var str2 = true
console.log(typeof (String(str2)), String(str2))
var str3 = false
console.log(typeof (String(str3)), String(str3))
var str4 = undefined
console.log(typeof (String(str4)), String(str4))
var str5 = null
console.log(typeof (String(str5)), String(str5))

变量+''

var str1 = 100
console.log(typeof (str1+''), str1+'')
var str2 = true
console.log(typeof (str2+''), str2+'')
var str3 = false
console.log(typeof (str3+''), str3+'')
var str4 = undefined
console.log(typeof (str4+''), str4+'')
var str5 = null 
console.log(typeof (str5+''), str5+'')