options: {
headers?: HttpHeaders | {[header: string]: string | string[]},
observe?: 'body' | 'events' | 'response',
params?: HttpParams|{[param: string]: string | number | boolean | ReadonlyArray<string | number | boolean>},
reportProgress?: boolean,
responseType?: 'arraybuffer'|'blob'|'json'|'text',
withCredentials?: boolean,
}
....
decrementScale() {
this.scale--;
document.documentElement.style.fontSize = this.scale + 'px';
}
incrementScale() {
this.scale++;
document.documentElement.style.fontSize = this.scale + 'px';
}