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Environment details

• OS: Windows
• Node.js version: 10.13.0
• npm version: 6.4.1
• @google-cloud/bigquery version: 2.0.1

Steps to reproduce

const dataset = BigQueryInstance.dataset("dataset");
await dataset.query({ query: "SELECT ... WHERE id =?", params: [ id ] });

Resultant error when attempting to execute

Error 
TypeError: Right-hand side of 'instanceof' is not an object
    at Function.getType_ (...\node_modules\@google-cloud\bigquery\build\src\index.js:462:1)

The production version, received from npm install, on the function "static getType_(value) {" has been compiled to

462:        else if (value instanceof big_js_1.default) {

this is "undefined"

and quite different to the

616:    } else if (value instanceof Big) {

of the source code.

The Big object is defined in the big_js_1 object, I am unsure why the compiler has done this?