字符转码btoa、atob

var str = 'javascript';

window.btoa(str)// "amF2YXNjcmlwdA=="

window.atob("amF2YXNjcmlwdA==")// "javascript"

二.对于转码来说，Base64转码的对象只能是单字节字符串，对于多字节的中文会报错如下：

var str = "China，中国"

window.btoa(str)

Uncaught DOMException: Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.

如果要支持中文这就要使用window.encodeURIComponent和window.decodeURIComponent

var str = "China，中国";

window.btoa(window.encodeURIComponent(str)) //"Q2hpbmElRUYlQkMlOEMlRTQlQjglQUQlRTUlOUIlQkQ="

window.decodeURIComponent(window.atob('Q2hpbmElRUYlQkMlOEMlRTQlQjglQUQlRTUlOUIlQkQ='))

//"China，中国"