js base64的转码与解码

使用方法window.btoa 将字符串转为base64编码

使用方法window.atob 将base64编码转为js字符串

 

 

var string = “Hello World”

let base64 = window.btoa(string)

let str = window.atob(base64)

 

  

注意：

javascript中的字符的实现一般是16位无符号整数

 

（http://www.ecma-international.org/ecma-262/5.1/#sec-15.5.1）

 

 

window.btoa接收的string是8位的，所以，如果是超过8位的，比如unicode编码 中的中文就会报错 

(

• btoa() accepts a “string” where each character represents an 8-bit byte – if you pass a string containing characters that can’t be represented in 8 bits, it willprobablybreak. This isn’t a problem if you’re actually treating the string as a byte array, but if you’re trying to do something else then you’ll have to encode it first.
  
• atob() returns a “string” where each character represents an 8-bit byte – that is, its value will be between 0 and 0xff. This does not mean it’s ASCII – presumably if you’re using this function at all, you expect to be working with binary data and not text.
  

)

 

let str = ‘我叫’

window.btoa(str) // InvalidCharacterError: String contains an invalid character

 

可以先将unicode text转换为utf-8编码（encodeURIComponent），然后使用base64编码，解码的时候再转换回来,就能得到原先的text

 

注意：

encodeURIComponent的转义范围比encodeURI更大