What am I doing wrong with my index.html?

I’m trying to implement what’s shown in the docs here: Unity - Manual: Cache behavior in WebGL

Seems really simple, and this is my full code (issue is at Line 63):

<!DOCTYPE html>
<html lang="en-us">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Unity WebGL Player | Online PC Builder</title>
    <link rel="shortcut icon" href="TemplateData/favicon.ico">
    <link rel="stylesheet" href="TemplateData/style.css">
    <link rel="manifest" href="manifest.webmanifest">
  </head>
  <body>
    <div id="unity-container">
      <canvas id="unity-canvas" width=960 height=540 tabindex="-1"></canvas>
      <div id="unity-loading-bar">
        <div id="unity-logo"></div>
        <div id="unity-progress-bar-empty">
          <div id="unity-progress-bar-full"></div>
        </div>
      </div>
      <div id="unity-warning"> </div>
    </div>
    <script>
      window.addEventListener("load", function () {
        if ("serviceWorker" in navigator) {
          navigator.serviceWorker.register("ServiceWorker.js");
        }
      });

      var container = document.querySelector("#unity-container");
      var canvas = document.querySelector("#unity-canvas");
      var loadingBar = document.querySelector("#unity-loading-bar");
      var progressBarFull = document.querySelector("#unity-progress-bar-full");
      var warningBanner = document.querySelector("#unity-warning");

      // Shows a temporary message banner/ribbon for a few seconds, or
      // a permanent error message on top of the canvas if type=='error'.
      // If type=='warning', a yellow highlight color is used.
      // Modify or remove this function to customize the visually presented
      // way that non-critical warnings and error messages are presented to the
      // user.
      function unityShowBanner(msg, type) {
        function updateBannerVisibility() {
          warningBanner.style.display = warningBanner.children.length ? 'block' : 'none';
        }
        var div = document.createElement('div');
        div.innerHTML = msg;
        warningBanner.appendChild(div);
        if (type == 'error') div.style = 'background: red; padding: 10px;';
        else {
          if (type == 'warning') div.style = 'background: yellow; padding: 10px;';
          setTimeout(function() {
            warningBanner.removeChild(div);
            updateBannerVisibility();
          }, 5000);
        }
        updateBannerVisibility();
      }

      var buildUrl = "Build";
      var loaderUrl = buildUrl + "/Builds.loader.js";
      var config = {
   // ...
#if USE_DATA_CACHING
   cacheControl: function (url) {
     // Disable explicit caching for all other files.
     // Note: the default browser cache may cache them anyway.
     return "no-store";
   },
#endif
   // ...
   dataUrl: buildUrl + "/Builds.data",
        frameworkUrl: buildUrl + "/Builds.framework.js",
        codeUrl: buildUrl + "/Builds.wasm",
        streamingAssetsUrl: "StreamingAssets",
        companyName: "DefaultCompany",
        productName: "Online PC Builder",
        productVersion: "0.1.0",
        showBanner: unityShowBanner,
}

      // By default Unity keeps WebGL canvas render target size matched with
      // the DOM size of the canvas element (scaled by window.devicePixelRatio)
      // Set this to false if you want to decouple this synchronization from
      // happening inside the engine, and you would instead like to size up
      // the canvas DOM size and WebGL render target sizes yourself.
      // config.matchWebGLToCanvasSize = false;

      if (/iPhone|iPad|iPod|Android/i.test(navigator.userAgent)) {
        // Mobile device style: fill the whole browser client area with the game canvas:
        var meta = document.createElement('meta');
        meta.name = 'viewport';
        meta.content = 'width=device-width, height=device-height, initial-scale=1.0, user-scalable=no, shrink-to-fit=yes';
        document.getElementsByTagName('head')[0].appendChild(meta);
      }

      loadingBar.style.display = "block";

      var script = document.createElement("script");
      script.src = loaderUrl;
      script.onload = () => {
        createUnityInstance(canvas, config, (progress) => {
          progressBarFull.style.width = 100 * progress + "%";
        }).then((unityInstance) => {
          loadingBar.style.display = "none";
        }).catch((message) => {
          alert(message);
        });
      };
      document.body.appendChild(script);
    </script>
  </body>
</html>

But when I run it in a browser, I get: Uncaught SyntaxError: Unexpected identifier ‘#if

This seems like a really basic error but as far as my not-HTML-optimized brain can tell, I’m doing exactly what the docs say.

Also, in case you’re wondering why I’m doing that, I’m trying to fix a bug where after a refresh, I get a “RuntimeError: call_indirect to a null table entry” error on my WebGL build when running on iOS 16.4 Safari…

EDIT: Changed my code to this:

var buildUrl = "Build";
var loaderUrl = buildUrl + "/Builds.loader.js";
var config = {
  dataUrl: buildUrl + "/Builds.data",
  frameworkUrl: buildUrl + "/Builds.framework.js",
  codeUrl: buildUrl + "/Builds.wasm",
  streamingAssetsUrl: "StreamingAssets",
  companyName: "DefaultCompany",
  productName: "Online PC Builder",
  productVersion: "0.1.0",
  showBanner: unityShowBanner,
};

// Conditional check to set cacheControl property
if (USE_DATA_CACHING) {
  config.cacheControl = function (url) { 
    return "no-store";
  };
}

But now I’m getting: Uncaught ReferenceError: USE_DATA_CACHING is not defined

#if USE_DATA_CACHING
#endif

This is C# specific. I cannot recall Javascript having such preprocessor directives. The symbol itself is a preprocessor (scripting define) symbol and thus not available in JS. I think that JS code in the manual is simply incorrect here. Try removing that check entirely, or write your own but with JS logic that gets the cache enabled state from the Unity API.

Turns out I was editing the wrong Index.html. There’s 1 in your build, and there’s one for your WebGL Template. The code works as written when editing the Template file. It seemed to make my loading on iOS much better but next morning, I’m stuck on a 90% load with no error message. My quest to get WebGL to run on iOS Safari continues…

Using C preprocessor #if/#endif blocks is compile-time extension that we have added to the WebGL Template files.

Those blocks are processed away during project build time according to the different checkboxes that were selected in the project build settings, so in the final index.html file they will no longer be present.

Does the “stuck on 90%” load state on iOS also happen in Development builds from local network? Which iOS Safari version are you on? I read recently that iOS 17 snuck in some new WebAssembly/WebGL regressions, which are currently being sorted out. (although there I think the error symptoms might have looked different: the page would load, but only later crash)