refactor(router-core): avoid creating promises when not necessary (#7582)

Author: Sheraff

packages/history/src/index.ts

@@ -340,7 +340,7 @@ export function createBrowserHistory(opts?: {
 
   // We need to track the current scheduled update to prevent
   // multiple updates from being scheduled at the same time.
-  let scheduled: Promise<void> | undefined
+  let scheduled: undefined | boolean
 
   // This function flushes the next update to the browser history
   const flush = () => {
@@ -363,7 +363,7 @@ export function createBrowserHistory(opts?: {
 
     // Reset the nextIsPush flag and clear the scheduled update
     next = undefined
-    scheduled = undefined
+    scheduled = false
     rollbackLocation = undefined
   }
 
@@ -391,7 +391,8 @@ export function createBrowserHistory(opts?: {
 
     if (!scheduled) {
       // Schedule an update to the browser history
-      scheduled = Promise.resolve().then(() => flush())
+      scheduled = true
+      queueMicrotask(() => flush())
     }
   }
 

packages/router-core/src/router.ts

@@ -2294,7 +2294,7 @@ export class RouterCore<
 
     // Clear pending location after commit starts
     // We do this on next microtask to allow synchronous navigate calls to chain
-    Promise.resolve().then(() => {
+    queueMicrotask(() => {
       if (this.pendingBuiltLocation === location) {
         this.pendingBuiltLocation = undefined
       }
@@ -2354,7 +2354,7 @@ export class RouterCore<
             `Blocked navigation to dangerous protocol: ${reloadHref}`,
           )
         }
-        return Promise.resolve()
+        return
       }
 
       // Check blockers for external URLs unless ignoreBlocker is true
@@ -2370,7 +2370,7 @@ export class RouterCore<
               action: 'PUSH',
             })
             if (shouldBlock) {
-              return Promise.resolve()
+              return
             }
           }
         }
@@ -2381,7 +2381,7 @@ export class RouterCore<
       } else {
         window.location.href = reloadHref
       }
-      return Promise.resolve()
+      return
     }
 
     return this.buildAndCommitLocation({