graphical output in code blocks

static/js/components/literate-programming/eval.js

@@ -0,0 +1,48 @@
+let outputIndex = 0;
+
+export function getOutputIndex() {
+    return outputIndex;
+}
+
+async function withTemporaryGlobalScope(callback) {
+    let state = {
+        oldValues: {},
+        set(key, value) {
+            this.oldValues[key] = globalThis[key];
+            globalThis[key] = value;
+        }
+    };
+    await callback(state);
+    for (let key in state.oldValues) {
+        globalThis[key] = state.oldValues[key];
+    }
+}
+
+export async function evaluate(commands) {
+    outputIndex = 0;
+    try {
+        await withTemporaryGlobalScope(async scope => {
+            for (let command of commands) {
+                if (command.kind == "module") {
+                    let blobUrl = URL.createObjectURL(new Blob([command.source], { type: "text/javascript" }));
+                    let module = await import(blobUrl);
+                    for (let exportedKey in module) {
+                        scope.set(exportedKey, module[exportedKey]);
+                    }
+                } else if (command.kind == "output") {
+                    ++outputIndex;
+                }
+            }
+        });
+    } catch (error) {
+        postMessage({
+            kind: "output",
+            output: {
+                kind: "error",
+                message: [error.toString()],
+            },
+            outputIndex,
+        });
+    }
+}
+