Decode Base64 with UCS-2 Encoding

I want to decode the Base64 result of MS-SQL Server in javascript, but I can’t find a true solution. I know SQL Server uses UCS-2 encoding, and I have to use the same encoding to decode in javascript.

For example, for MwZEBicGRQY= the encoded result must be سلام.

Do you have any solution to decode that using javascript?