What prevents `console.log` from working within a button click event?

Why is this not functioning correctly?

<button (click)="console.log('ok');">Display Details</button>

The error message reads:

Cannot read property 'log' of undefined

However, a console.log statement in the class constructor works as expected:

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app3-directives',
  templateUrl: './directives.component.html'
})
export class DirectivesComponent implements OnInit {

  constructor() { console.log('start') }

  ngOnInit() {
  }

}

...the 'start' message does print in the console. So why is the button showing it as undefined?

Answer №1

In the template, the console object is not recognized as a public property of the component. One way to make it accessible in the template is by including it as a property within the component:

export class DirectivesComponent implements OnInit {

  // Exposing console for use in the template
  console = console;

  constructor() { console.log('start') }

  ngOnInit() {
  }
}

However, this method is not recommended for logging purposes. Logging should primarily be used for development and debugging. A better approach would be to keep the logging logic within the component, triggered conditionally based on whether the application is running in development mode:

import { isDevMode } from '@angular/core';

...

click() {
  if (isDevMode()) {
    console.log('Performing some logging');
  }
}

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