monitor-adapter.js -- implement JSON support

src/lib/monitor-adapter.js

@@ -2,6 +2,17 @@ import OpcodeLabels from './opcode-labels.js';
 
 const isUndefined = a => typeof a === 'undefined';
 
+const circularReplacer = () => {
+    const stack = new Set();
+    return function replacer(key, value) {
+        if (typeof value === "object" && value !== null) {
+            if (stack.has(value)) return Array.isArray(value) ? "[...]" : "{...}";
+            stack.add(value);
+        }
+        return value;
+    };
+};
+
 /**
  * Convert monitors from VM format to what the GUI needs to render.
  * - Convert opcode to a label and a category
@@ -32,18 +43,26 @@ export default function ({id, spriteName, opcode, params, value, vm}) {
         value = Number(value.toFixed(6));
     }
 
-    // Turn the value to a string, for handle boolean values
+    // Turn the value to a string, to handle boolean values
     if (typeof value === 'boolean') {
         value = value.toString();
     }
 
-    // Lists can contain booleans, which should also be turned to strings
+    // Turn the value to a string, to handle JSON values
+    // do not convert arrays as it will be confused for lists
+    if (typeof value === 'object' && !Array.isArray(value)) {
+        value = JSON.stringify(value, circularReplacer);
+    }
+
+    // Lists can contain booleans or Objects, which should also be turned to strings
     if (Array.isArray(value)) {
         value = value.slice();
         for (let i = 0; i < value.length; i++) {
             const item = value[i];
             if (typeof item === 'boolean') {
                 value[i] = item.toString();
+            } else if (typeof value[i] === 'object' && !Array.isArray(value[i])) {
+                value[i] = JSON.stringify(item, circularReplacer);
             }
         }
     }