How can I create a const assignment in a typescript transformer?

Question

I can create a variable assignment with this code:

ts.createVariableStatement(undefined, 
     [ts.createVariableDeclaration('a', undefined, 
      ts.createStringLiteral('42'))])

/// yields: var a = 42

I cannot however create a const assignment. I am quite sure it should work like so:

ts.createVariableStatement([ts.createModifier(ts.SyntaxKind.ConstKeyword)], 
     [ts.createVariableDeclaration('a', undefined, 
      ts.createStringLiteral('42'))])

but this yields an error:

[!] Error: Unexpected keyword 'var'

an no javascript is emitted due to that error. The error message is very confusing as well.

Answer 1

Try this:

ts.createVariableStatement(
      [],
      ts.createVariableDeclarationList(
        [
          ts.createVariableDeclaration(
            'a',
            undefined,
            ts.createStringLiteral('42'),
          ),
        ],
        ts.NodeFlags.Const,
      ),
    )

Based on this answer.