How do I control the name of a function?

[stroiman]

I'm building a headless browser in Go, and not knowing about this, started using the v8 engine (have basic HTMX app with a bit of interactivity supported).

However, upon discovering this project, I immediately started looking into using goja instead of v8; having a native Go implementation (now I'm glad I decided to keep the DOM decoupled from the script engine)

But exposing native Go objects to JS is not enough. They must adhere to the DOM standard, e.g. an <input> must be an instance of HTMLInputElement, which is also an HTMLElement, Element, Node, EventTarget, and of course Object.

And I'm a little puzzled how I setup this correctly.

Already just at setting up the globals scope, I ran into issues, just having constructors have the right name. E.g., Window.name should be Window

func WindowConstructor(call goja.ConstructorCall, r *goja.Runtime) (*goja.Object, error) {
	// Don't know if this is right goja-wise. But Window _is_ a class, but try to construct one gives a TypeError in JS.
	panic(r.NewTypeError("Illegal Constructor")) 
}

func (d *GojaDriver) NewScriptEngine(window html.Window) html.ScriptEngine {
	vm := goja.New()
	globalThis := vm.GlobalObject()
	globalThis.Set("window", globalThis)
	globalThis.Set("Window", WindowConstructor)
	return &GojaInstance{
		vm: vm,
	}
}

Checking with gomega reveals a different name.

		Expect(window.Eval("Window.name")).To(Equal("Window"), "Window.name")

This fails with

  [FAILED] Window.name
  Expected
      <string>: github.com/stroiman/go-dom/browser/goja-driver.WindowConstructor
  to equal
      <string>: Window

Next attempt was to get the get a function object for the function, and explicitly set the name property.

	Window := vm.ToValue(WindowConstructor).(*goja.Object)
	Window.Set("name", "Window")
	globalThis.Set("Window", Window)

But this produces the same result. In JS, Window.name is still github.com/stroiman/go-dom/browser/goja-driver.WindowConstructor - not Window - as it should be.

How do I make sure that the function objects have the right name?

[dop251]

The name property in a function is defined as non-writable, however it is configurable which means you can redefine it with Window.DefineDataProperty("name", vm.ToValue("Window"), FLAG_NOT_SET, FLAG_NOT_SET, FLAG_NOT_SET)

[stroiman]

Ah, of course, you can't change it after the fact in JS either. Thanks for the input.

Would it make sense to provide a way to control it before setting it?

p.s., for what it's worth, the way I used v8 so far, the function name is set to the name I assign it in global scope.