javascript 使用btoa和atob来进行Base64转码和解码

javascript原生的api本来就支持,Base64,但是由于之前的javascript局限性，导致Base64基本中看不中用。当前html5标准正式化之际，Base64将有较大的转型空间,对于Html5 Api中出现的如FileReader Api, 拖拽上传,甚至是Canvas,Video截图都可以实现。

好了，前言说了一大堆，开发者需要重视：

一.我们来看看，在javascript中如何使用Base64转码

var str = 'javascript';

window.btoa(str)
//转码结果 "amF2YXNjcmlwdA=="

window.atob("amF2YXNjcmlwdA==")
//解码结果 "javascript"

二.对于转码来说，Base64转码的对象只能是字符串，因此来说，对于其他数据还有这一定的局限性，在此特别需要注意的是对Unicode转码。

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.

很明显，这种方式是不行的，那么如何让他支持汉字呢，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"

window.btoa('{"success":true,"msg":null,"errorCode":0,"data":{"memberId":"6976462","canBxMoney":0,"bxdAsset":3000.00,"bxdProfit":95.752732}}');
"eyJzdWNjZXNzIjp0cnVlLCJtc2ciOm51bGwsImVycm9yQ29kZSI6MCwiZGF0YSI6eyJtZW1iZXJJZCI6IjY5NzY0NjIiLCJjYW5CeE1vbmV5IjowLCJieGRBc3NldCI6MzAwMC4wMCwiYnhkUHJvZml0Ijo5NS43NTI3MzJ9fQ=="

window.atob("eyJzdWNjZXNzIjp0cnVlLCJtc2ciOm51bGwsImVycm9yQ29kZSI6MCwiZGF0YSI6eyJtZW1iZXJJZCI6IjY5NzY0NjIiLCJjYW5CeE1vbmV5IjowLCJieGRBc3NldCI6MzAwMC4wMCwiYnhkUHJvZml0Ijo5NS43NTI3MzJ9fQ==")
"{"success":true,"msg":null,"errorCode":0,"data":{"memberId":"6976462","canBxMoney":0,"bxdAsset":3000.00,"bxdProfit":95.752732}}"