function registerKeyHandlers () {
    let toolbar =  $("#toolbarContainer").dxToolbar("instance");
    toolbar.registerKeyHandler("backspace", function (e) {
        // The argument "e" contains information on the event
    });
    toolbar.registerKeyHandler("space", function (e) {
        // ...
    });
}

import { ..., ViewChild, AfterViewInit } from '@angular/core';
import { DxToolbarModule, DxToolbarComponent } from 'devextreme-angular';
// ...
export class AppComponent implements AfterViewInit {
    @ViewChild(DxToolbarComponent) toolbar: DxToolbarComponent
    ngAfterViewInit () {
        this.toolbar.instance.registerKeyHandler("backspace", function (e) {
            // The argument "e" contains information on the event
        });
        this.toolbar.instance.registerKeyHandler("space", function (e) {
            // ...
        });
    }
}
@NgModule({
    imports: [
        // ...
        DxToolbarModule
    ],
    // ...
})