docs(aio): Clearing array with [] (#20369) (#20395)

Clearing array with setting length to 0 replaced with [] for being short
and marginally efficient. For reference: [] is turned into a sequence of
around 15 machine instructions on x64 (if bump pointer allocation succeeds),
whereas a.length=0 is a C++ runtime function call, which requires 10-100x as
many instructions.
Benedikt Meurer

PR Close #20395

aio/content/examples/lifecycle-hooks/src/app/after-content.component.ts

@@ -108,7 +108,7 @@ export class AfterContentParentComponent {
   }
 
   reset() {
-    this.logs.length = 0;
+    this.logs = [];
     // quickly remove and reload AfterContentComponent which recreates it
     this.show = false;
     this.logger.tick_then(() => this.show = true);

aio/content/examples/lifecycle-hooks/src/app/after-view.component.ts

@@ -110,7 +110,7 @@ export class AfterViewParentComponent {
   }
 
   reset() {
-    this.logs.length = 0;
+    this.logs = [];
     // quickly remove and reload AfterViewComponent which recreates it
     this.show = false;
     this.logger.tick_then(() => this.show = true);

aio/content/examples/lifecycle-hooks/src/app/counter.component.ts

@@ -27,7 +27,7 @@ export class MyCounterComponent implements OnChanges {
     // Empty the changeLog whenever counter goes to zero
     // hint: this is a way to respond programmatically to external value changes.
     if (this.counter === 0) {
-      this.changeLog.length = 0;
+      this.changeLog = [];
     }
 
     // A change to `counter` is the only change we care about

aio/content/examples/lifecycle-hooks/src/app/do-check.component.ts

@@ -68,7 +68,7 @@ export class DoCheckComponent implements DoCheck {
 
   reset() {
     this.changeDetected = true;
-    this.changeLog.length = 0;
+    this.changeLog = [];
   }
 }
 

aio/content/examples/lifecycle-hooks/src/app/logger.service.ts

@@ -18,7 +18,7 @@ export class LoggerService {
     }
   }
 
-  clear() { this.logs.length = 0; }
+  clear() { this.logs = []; }
 
   // schedules a view refresh to ensure display catches up
   tick() {  this.tick_then(() => { }); }

aio/content/examples/lifecycle-hooks/src/app/on-changes.component.ts

@@ -43,7 +43,7 @@ export class OnChangesComponent implements OnChanges {
   }
   // #enddocregion ng-on-changes
 
-  reset() { this.changeLog.length = 0; }
+  reset() { this.changeLog = []; }
 }
 
 /***************************************/

aio/content/examples/lifecycle-hooks/src/app/spy.component.ts

@@ -34,7 +34,7 @@ export class SpyParentComponent {
   }
   reset() {
     this.logger.log('-- reset --');
-    this.heroes.length = 0;
+    this.heroes = [];
     this.logger.tick();
   }
 }

aio/content/examples/toh-pt4/src/app/message.service.ts

@@ -9,6 +9,6 @@ export class MessageService {
   }
 
   clear() {
-    this.messages.length = 0;
+    this.messages = [];
   }
 }

aio/content/examples/toh-pt5/src/app/message.service.ts

@@ -9,6 +9,6 @@ export class MessageService {
   }
 
   clear() {
-    this.messages.length = 0;
+    this.messages = [];
   }
 }

aio/content/examples/toh-pt6/src/app/message.service.ts

@@ -9,6 +9,6 @@ export class MessageService {
   }
 
   clear() {
-    this.messages.length = 0;
+    this.messages = [];
   }
 }

aio/content/examples/universal/src/app/message.service.ts

@@ -9,6 +9,6 @@ export class MessageService {
   }
 
   clear() {
-    this.messages.length = 0;
+    this.messages = [];
   }
 }