Phaser 3: Finish loading json before Scene.preload() gets called - phaser-framework

Question

I want to describe my scenes in a JSON file, and then preload images etc. according to the contents of that JSON file. So the content of the JSON file needs to have been fully loaded before entering preload. I don't know how to do this. I've created a minimal, reproducible jsfiddle that logs preload: undefined when prepreload = true.
For prepreload = false I get create: [object Object].
var prepreload = true
var config = { scene: { init: init, preload: preload, create: create } }
var game = new Phaser.Game(config)
function init(config) {
if (prepreload) {
this.load.json('scenedata', 'scene.json');
this.load.start();
}
}
function preload () {
if (prepreload)
console.log(this.cache.json.get("scenedata"));
else
this.load.json('scenedata', 'scene.json');
}
function create () {
if (!prepreload)
console.log(this.cache.json.get("scenedata"));
}
Any idea how to preload images according to the contents of a JSON file - ideally all inside the Scene class, rather than doing it externally and passing it into the init method or similar.

Answer 1

SettingsConfig can be used for that - the files listed under pack will already have been loaded when entering the init method.
Here's how it can be done (Phaser 3.55.2):
var config = {
scene: {
init: init,
preload: preload,
create: create,
pack: {
"files": [
{ type: 'json', key: 'scene', url: 'scene.json' }
}
}
}
}
var game = new Phaser.Game(config)
Here's a slightly different variant, using TypeScript:
export class TestScene extends Phaser.Scene {
constructor() {
super({ pack: {
"files": [ { type: 'json', key: 'scene', url: 'scene.json' }