[JS] Expand JavaScript implementation

[asfimport]

Reporter: Wes McKinney / @wesm
Assignee: Paul Taylor / @trxcllnt

Related issues:

• [JS] Use flatc to generate TypeScript (contains)

_{Note: This issue was originally created as ARROW-1479. Please see the migration documentation for further details.}

[asfimport]

Paul Taylor / @trxcllnt:
PR submitted: #1062

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 1062
#1062