In Kotlin/JS Multiplatform. trying to call `window.onload()` ```window.onload { val canvas = doc...

# getting-started

[Ray Rahke]

In Kotlin/JS Multiplatform. trying to call window.onload()

window.onload { 
  val canvas = document.getElementById("canvas")
}

getting error

Task :compileKotlinJs FAILED
e: Reference has a nullable type '((Event) -> dynamic)?', use explicit '?.invoke()' to make a function-like call instead
e: Type mismatch: inferred type is () -> Unit but Event was expected

What is the syntax for this?

I tried window?.invoke().onload { and that also got an error

[Ruckus]

I think you need window.onload?.invoke { ... }

It's onload that's nullable, not window.

https://kotlinlang.org/api/latest/jvm/stdlib/org.w3c.dom/-global-event-handlers/

[Ray Rahke]

ahk thanks

[Darryl Miles]

Hmm I just debugged an issue that needed to check:

fun windowOnLoadOrTimeout(function: ((Event?) -> Unit)) {
  if(document.body != null) {  // late we missed "load" event
    window.setTimeout({
      function.invoke(null)
      null  // lambda return is fussy here
    }, 0)
  } else {
    window.addEventListener("load") { event ->  // early need to wait for "load" event
      function.invoke(event)
    }
  }
}

windowOnLoadOrTimeout() {
   // my work here
}

The purpose of this, is that it will always run, even when it missed the window "load" event

[Ray Rahke]

@Ruckus I do that now, but I am getting an error Type mismatch: inferred type is () -> Unit but Event was expected

[Ray Rahke]

window.onload.invoke() { 
  ...
}

[Darryl Miles]

if you can debug the reason setTimeout() does not work https://pl.kotl.in/Dx8U87Xhk then my original code more or less runs

[Darryl Miles]

Your playground code does not use window.onload.invoke() {}