to-fast-properties 
Force V8 to use fast properties for an object
Use %HasFastProperties(object)
and --allow-natives-syntax
to check whether an object already has fast properties.
Install
$ npm install to-fast-properties
Usage
const toFastProperties = require('to-fast-properties');
const object = {
foo: true,
bar: true
};
delete object.foo;
// `object` now has slow properties
toFastProperties(object);
// `object` now has fast properties