使用Blob从ArrayBuffer构造文件

I am experimenting some HTML5 APIs like FileReader, Blob and etc. I am trying to slice a file into chunks, read each chunk as array buffer, create a blob by adding all the chunked array buffers together, and then reconstruct the file. The issue i am having is after reconstruct the file, the file is corrupted for most file types except for text files which are fine. Any idea why? Below is the code i have so far.I am experimenting some HTML5 APIs like FileRea