Look very ambiguous as to what you have is it an array or buffer?
From array using JS in function node.
msg.payload = String.fromCharCode.apply(null, msg.payload);
returns HILSCHYW
When supplying data it is best to supply text. You can gain this by using the copy value in the debug sidebar
There’s a great page in the docs (Working with messages : Node-RED) that will explain how to use the debug panel to find the right path/value for any data item.
Pay particular attention to the part about the buttons that appear under your mouse pointer when you over hover a debug message property in the sidebar.
Then paste in thread using
In order to make code readable and usable it is necessary to surround your code with three backticks (also known as a left quote or backquote ```)
```
code goes here
```
You can edit and correct your post by clicking the pencil 
icon.
See this post for more details - How to share code or flow json
Or have a look at node-red-contrib-buffer-parser (node) - Node-RED
