add maxWaitMs argument

AxeObserver.js

@@ -9,12 +9,34 @@ const requestIdleCallback =
   }
 
 // Define own debounce function to avoid excess dependencies
-// Ref: https://chrisboakes.com/how-a-javascript-debounce-function-works/
-function debounce(callback, wait) {
+function debounce(callback, debounceMs, maxWaitMs) {
   let timeout
+  let queuedSince
   return (...args) => {
     clearTimeout(timeout)
-    timeout = setTimeout(() => callback.apply(this, args), wait)
+
+    const isExecutionAlreadyQueued = !!queuedSince
+
+    if (!isExecutionAlreadyQueued) {
+      queuedSince = Date.now()
+    }
+
+    const execute = () => {
+      queuedSince = null
+      return callback.apply(this, args)
+    }
+
+    const queueExecution = () => {
+      timeout = setTimeout(execute, debounceMs)
+    }
+
+    const isMaxDelayExceeded = Date.now() - queuedSince > maxWaitMs
+
+    if (isMaxDelayExceeded) {
+      execute()
+    } else {
+      queueExecution()
+    }
   }
 }
 
@@ -53,14 +75,15 @@ export default class AxeObserver {
 
     axeCore.configure(axeConfiguration)
   }
-  observe(targetNode, debounceMs = 1000) {
+  observe(targetNode, debounceMs = 1000, maxWaitMs = debounceMs * 10) {
     if (!targetNode) {
       throw new Error('AxeObserver.observe requires a targetNode')
     }
 
     const scheduleAudit = debounce(
       () => requestIdleCallback(() => this._auditTargetNode(targetNode)),
-      debounceMs
+      debounceMs,
+      maxWaitMs
     )
     const mutationObserver = new window.MutationObserver(scheduleAudit)
 

README.MD

@@ -39,7 +39,8 @@ The `AxeObserver` constructor takes two parameters:
 The `AxeObserver.observe` method takes two parameters:
 
 - `targetNode` (required). The node that should be observed & analyzed.
-- `debounceMs` (optional, defaults to `1000`). The number of milliseconds to wait for component updates to cease before performing an analysis of all the changes.
+- `debounceMs` (optional, defaults to `1000`). The number of milliseconds that updates should cease before an analysis is performed.
+- `maxWaitMs` (optional, defaults to `debounceMs * 10`). Number of milliseconds after which an analysis will be performed, even if the targetNode is still updating.
 
 ## Credits