While learning DynamoDB, after a ton of tutorials and documentation, the moment it made click was when I saw the next table in the AWS SDK source code:
| JavaScript Type | DynamoDB AttributeValue |
|:-------------------------------------:|-------------------------|
| String | S |
| Number | N |
| Boolean | BOOL |
| null | NULL |
| Array | L |
| Object | M |
| Buffer, File, Blob, ArrayBuffer, | B |
| DataView, and JavaScript typed arrays | |