Publish directory

publish/wwwroot/js/reload.js

@@ -0,0 +1,84 @@
+const scriptKeys = new Set();
+
+export function onUpdate() {
+    // determine if this is an initial request
+    let initialRequest = scriptKeys.size === 0;
+
+    // iterate over all script elements in document
+    const scripts = document.getElementsByTagName('script');
+    for (const script of Array.from(scripts)) {
+        // only process scripts that include a data-reload attribute
+        if (script.hasAttribute('data-reload')) {
+            let key = getKey(script);
+
+            if (!initialRequest) {
+                // reload the script if data-reload is "always" or "true"... or if the script has not been loaded previously and data-reload is "once"
+                let dataReload = script.getAttribute('data-reload');
+                if ((dataReload === 'always' || dataReload === 'true') || (!scriptKeys.has(key) && dataReload == 'once')) {
+                    reloadScript(script);
+                }
+            }
+
+            // save the script key
+            if (!scriptKeys.has(key)) {
+                scriptKeys.add(key);
+            }
+        }
+    }
+}
+
+function getKey(script) {
+    if (script.src) {
+        return script.src;
+    } else if (script.id) {
+        return script.id;
+    } else {
+        return script.innerHTML;
+    }
+}
+
+function reloadScript(script) {
+    try {
+        if (isValid(script)) {
+            injectScript(script);
+        }
+    } catch (error) {
+        console.error(`Blazor Script Reload failed to load script: ${getKey(script)}`, error);
+    }
+}
+
+function isValid(script) {
+    if (script.innerHTML.includes('document.write(')) {
+        console.log(`Blazor Script Reload does not support scripts using document.write(): ${script.innerHTML}`);
+        return false;
+    }
+    return true;
+}
+
+function injectScript(script) {
+    return new Promise((resolve, reject) => {
+        var newScript = document.createElement('script');
+
+        // replicate attributes and content
+        for (let i = 0; i < script.attributes.length; i++) {
+            if (script.attributes[i].name !== 'data-reload') {
+                newScript.setAttribute(script.attributes[i].name, script.attributes[i].value);
+            }
+        }
+        newScript.nonce = script.nonce; // must be referenced explicitly
+        newScript.innerHTML = script.innerHTML;
+
+        // dynamically injected scripts cannot be async or deferred
+        newScript.async = false;
+        newScript.defer = false;
+
+        newScript.onload = () => resolve();
+        newScript.onerror = (error) => reject(error);
+
+        // inject script element in head to force execution in Blazor
+        document.head.appendChild(newScript);
+
+        // remove data-reload attribute
+        script.removeAttribute('data-reload');
+    });
+}