Minify internal JS class helper method properties

[mattscotty]

I've just been looking at the minified output from a class I've just wrote and it seems the internal property names are not being minified. If they're an internal function (not accessible externally), its possible these could be minified to single letters too. An example is as follows;

` const ExampleA = (function () { class exampleA extends HTMLElement { constructor() { super(); }

        connectedCallback() {
            this.exampleMethod();
        }

        exampleMethod() {
            function helperMethod(opts = { opt1, opt2, opt3, opt4, opt5 }) {
                //Do something
            }

            helperMethod({
                opt1: 'Example1',
                opt2: 'Example2',
                opt3: 'Example3',
                opt4: 'Example4',
                opt5: 'Example5'
            });
        }
    }

    customElements.define('example-a', ExampleA);

    return exampleA;
}());

`

From what I can tell, both the declarations in helperMethod, and usage of those properties (e.g. opt1, opt2...), could be minified(?)