Angular 2 - style component on another components button click

in child template:

<div class="element1" #element1 ></div>

in child component:

@ViewChild('element1') element1: ElementRef;

in parent:

@ViewChild(ChildComponent) child: ChildComponent;

constructor(private renderer: Renderer2) {}

hideElement() {
  this.renderer.setStyle(child.element1 , 'visibility' , 'hidden');
}

Method 1 - Parent-child relationship

You can hide or show the div in the child component with a hideDiv property, and make that property available for data binding with the @Input decorator. The property can toggle the visibility style directly or apply a class to the div:

@Component({
  selector: 'child-component',
  template: `
    <div></div>
    <div [class.hiddenClass]="hideDiv"></div>
    <div [style.visibility]="hideDiv ? 'hidden' : 'visible'"></div>
    <div></div>
  `,
  styles: [`.hiddenClass { visibility: hidden; }`]
})
export class ChildComponent {
  @Input() hideDiv = false;
}

You would then modify it with data binding when clicking on the button in the parent component:

@Component({
  selector: 'parent-component',
  template: `
    <button (click)="hideChildDiv = !hideChildDiv">Toggle div visibility</button>
    <child-component [hideDiv]="hideChildDiv" ></child-component>
  `
})
export class ParentComponent {
  hideChildDiv = false;
}

You can test the code in this stackblitz.

Method 2 - Communication between two components with a service

You can use a service to allow two separate components to communicate with each other or to share some information. See this stackblitz for a demo.

Service:

import { Injectable } from "@angular/core"

@Injectable()
export class VisibilityService {
  hideDiv = false;
}

Parent component:

@Component({
  selector: 'app-root',
  template: `
    <child1></child1>
    <child2></child2>
  `
})
export class AppComponent {
}

Child1 component:

import { VisibilityService } from "./visibility.service";

@Component({
  selector: 'child1',
  template: `
    <button (click)="hideDiv = !hideDiv">Toggle div visibility</button>
  `
})
export class Child1Component {

  public get hideDiv(): boolean {
    return this.visibilityService.hideDiv;
  }

  public set hideDiv(value: boolean) {
    this.visibilityService.hideDiv = value;
  }

  constructor(private visibilityService: VisibilityService) { }
}

Child2 component:

import { VisibilityService } from "./visibility.service";

@Component({
  selector: 'child2',
  template: `
    <div class="div1"></div>
    <div class="div1" [class.hiddenClass]="hideDiv"></div>
    <div class="div1"></div>
    <div class="div1" [style.visibility]="hideDiv ? 'hidden' : 'visible'"></div>
    <div class="div1"></div>
  `
})
export class Child2Component {

  public get hideDiv(): boolean {
    return this.visibilityService.hideDiv;
  }

  constructor(private visibilityService: VisibilityService) { }
}

Module:

...

import { AppComponent } from './app.component';
import { Child1Component } from './child1.component';
import { Child2Component } from './child2.component';
import { VisibilityService } from "./visibility.service";

@NgModule({
  declarations: [ 
    AppComponent,
    Child1Component,
    Child2Component
  ],
  providers: [
    VisibilityService
  ],
  ...
})
export class AppModule { }