Angular Lifecycle Debugging Logger

Decorator to quickly add logging for Angular lifecycle hooks in your components

Minimal markup - no more adding console logs to see what your components are doing!

Installation

npm install --save-dev ng-lifecycle-debug

Usage

import { DebugLifeCycle } from 'ng-lifecycle-debug';

@DebugLifeCycle()
@Component({
  selector: 'app-sheep-stacker',
  templateUrl: './sheep-stacker.component.html',
  styleUrls: ['./sheep-stacker.component.scss']
})
export class SheepStackerComponent implements OnInit, OnChanges {

  @Input() initialStack: number;
  private initialStack$: BehaviorSubject<number>;
  sheepCount$: Observable<number>;

  public ngOnInit(): void {
    this.initialStack$ = new BehaviorSubject<number>(this.initialStack);
    this.sheepCount$ = this.initialStack$.asObservable().pipe(
      switchMap((count) => interval(1000).pipe(map((val) => val + count)))
    );
  }

  public ngOnChanges(changes: SimpleChanges): void {
    if (changes['initialStack'] && !isNaN(+changes['initialStack'].currentValue)) {
      this.initialStack$ && this.initialStack$.next(changes.initialStack.currentValue);
    }
  }

}

// -- Console Output --
// ngOnChanges called for SheepStackerComponent
//    initialStack changed from undefined to 1
// ngOnInit called for SheepStackerComponent
// ngAfterViewInit called for SheepStackerComponent

@DebugLifeCycle('ngOnInit')
// -- Console Output --
// ngOnInit called for SheepStackerComponent

@DebugLifeCycle(['ngOnInit','ngAfterViewInit'])
// -- Console Output --
// ngOnInit called for SheepStackerComponent
// ngAfterViewInit called for SheepStackerComponent

@DebugLifeCycle((hook, className) => console.log(`Awesome ${hook} happened in ${className}`))
// -- Console Output --
// Awesome ngOnChanges happened in SheepStackerComponent
// Awesome ngOnInit happened in SheepStackerComponent
// Awesome ngAfterViewInit happened in SheepStackerComponent

@DebugLifeCycle({hooks: ['ngOnInit','ngAfterViewInit'], logFunc: (hook, className) => console.log(`Awesome ${hook} happened in ${className}`)})
// -- Console Output --
// Awesome ngOnInit happened in SheepStackerComponent
// Awesome ngAfterViewInit happened in SheepStackerComponent

@DebugLifeCycle({hooks: ['ngOnInit','ngAfterViewInit'], logFuncMap: { ngOnInit: () => console.log('Something happened')}})
// -- Console Output --
// Something happened
// ngAfterViewInit called for SheepStackerComponent

Options

Defaults

Default options are to log the ngOnInit, ngOnChanges, ngAfterViewInit, and ngOnDestroy lifecycle hooks using a simple console.log, with a more advanced version using console.group for ngOnChanges.

Simple Options

The decorator accepts simplified options for quicker and more limited use:

Option	Description
string	log a specific lifecycle hook
string[]	log a specific subset of lifecycle hooks
function	a function to use for all logging

Note that the default function map (that has a different output for ngOnChanges) is still used if a function is given as a single argument. To override this, use the advanced options with logFunc and pass an empty object as the logFuncMap.

Advanced Options

Options are passed as an object with one or more of the following keys:

Option	Description
hooks: string[]	array of Angular lifecycle hooks to respond to
logFunc: Function	specify a custom function for each hook
logFuncMap: Object	specify different functions for different lifecycle hooks, where the object key is the hook and the value is the function

Note: the default function map (that has a different output for ngOnChanges) is still used if a function is given as a single argument. For overriding it when

Option Types and Interfaces

Type / Interface	Description
DebugLifeCycleHook	String values for Angular lifecycle hooks
DebugLogFunction	Function required for logging (hook, class, ...args)
DebugLogFunctionMap	Object for lifecycle hook to function map
DebugLifeCycleOptionObject	Overall configuration object

To Do

• Add optional logging of component properties
• Add capability for enter / exit logging