https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding
In JavaScript there are two functions respectively for decoding and encoding base64 strings:
工作场景，客户端HTML片段的保存与再现。
HTML5 Base64_encoding_and_decoding
原文：http://www.cnblogs.com/rgqancy/p/7409933.html