Using "this" keyword inside bind function

[Tekameikite]

I have a bind function like this:

ui.Bind("changeTheme", func() {
      colors := ui.Eval(`document.getElementsByTagName("span")[0].getAttribute("style");`)
      fmt.Println("Colors:", colors)`})

What I need is an element like this:

<div onclick="changeTheme(this)">
<span style="color:#000000;background-color:#FFFF00">foo</span>
</div>

and coresponding function:

function changeColor(element) {
          var theme= element.getElementsByTagName("span")[0].getAttribute("style");
          console.log(theme)
      }

I have to get "theme" element and assign it to a variable in Go

I tried doing it like this with the same html element but it's not working

ui.Bind("changeTheme", func(element lorca.Value) {
      colors := ui.Eval(`element.getElementsByTagName("span")[0].getAttribute("style");`)
      fmt.Println("Colors:", colors)
  })

[Tekameikite]

<div onclick="changeTheme(518)">
<span style="color:#000000;background-color:#FFFF00">foo</span>
</div>

```go
ui.Bind("changeTheme", func(index int) {
      colors := ui.Eval(fmt.Sprintf(`document.getElementsByTagName("span")>[%v].getAttribute("style");`, index)).String()
      fmt.Println("Colors:", colors)
  })

I basically got it to work like that with the index of span element but I have like 518 elements that use this function so it's not that efficient compared to using "this" keyword