Merge pull request #4 from ccri/empty-table

Fix exception for empty Table

Author: trxcllnt

js/src/table.ts

@@ -101,7 +101,9 @@ export class Table implements DataFrame {
  }
  this.schema = schema;
  this.batches = batches;
- this.batchesUnion = batches.reduce((union, batch) => union.concat(batch));
+ this.batchesUnion = batches.length == 0 ?
+ new RecordBatch(schema, 0, []) :
+ batches.reduce((union, batch) => union.concat(batch));
  this.length = this.batchesUnion.length;
  this.numCols = this.batchesUnion.numCols;
  }

js/test/unit/table-tests.ts

@@ -24,6 +24,10 @@ const {
 } = Arrow;
 
 describe(`Table`, () => {
+ test(`can create an empty table`, () => {
+ expect(Table.empty().length).toEqual(0)
+ });
+
  describe(`single record batch`, () => {
  const table = Table.from({
  'schema': {