vanjs-org.github.io/assert/code/gc-derive.html at b3c6994aab0bf78fb9d9945f5e5f0fb82f09603a · vanjs-org/vanjs-org.github.io · GitHub

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<!DOCTYPE html>
<html>
  <head>
    <link rel="icon" href="/logo.svg">
    <title>Demo for Garbage Collection (Bad Example for Derived State)</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
  </head>
  <body>
    <script type="text/javascript" src="van-latest.nomodule.js"></script>
    <script>
      const {div, h4, input, pre, span} = van.tags

      const renderPre = van.state(false)
      const prefix = van.state("Prefix")
      const TextDiv = () => div(() => {
        const suffix = van.state("Suffix")
        const text = van.derive(() => `${prefix.val} - ${suffix.val}`)
        return (renderPre.val ? pre : span)(text)
      })

      van.add(document.body,
        div(
          "renderPre: ",
          input({type: "checkbox", checked: renderPre, onclick: e => renderPre.val = e.target.checked}),
          " prefix: ",
          input({type: "text", value: prefix, oninput: e => prefix.val = e.target.value}),
        ),
        h4("Rendering Result:"),
        TextDiv(),
      )
    </script>
  </body>
</html>