Why a click() function triggers twice for the custom component in Angular 2?

Because you have bound it twice on the child component and on the parent component. The mouseEvent propagates from the child component to the parent component by default. You can stop propagation of event to parent component.

Template:

<div (click)="divClick($event)">Custom Div Clcik here!</div>

Class:

divClick(event) {
    event.stopPropagation();
    alert("divClick");
}

Your problem is that you call click() event on your parent component and in your child component: here:

<cus-div (click)="onClick()"></cus-div>

and here:

<div (click)="divClick()">Custom Div Clcik here!</div>

remove the click event on your <cus-div></cus-div> of your click event and it will trigger once

i had a similar issue, i found the solution for mine, i had two *ngIf, one negated, to swap a icon in my case. I replaced *ngIf with [hidden] (display: none;).

Try:

event.preventDefault();

instead of:

event.stopPropagation();

my believe is: add emit solves it as well

Template

<div (click)="divClick($event)">Custom Div Clcik here!</div>

Class

@Output()
divClick = new EventEmitter<any>().emit;