Angular interceptor exclude specific urls

I am writing interceptors such that I don’t have to handle the headers in every service calling my web api. The problem with this is that 99% of my calls require 1 specific set of headers, but the other 1% only require 1 of the headers and will not work with the others present. With this being known my idea is to make 2 interceptors, the first will add the 1 header that they all use and the second will add the rest of the headers, with the second excluding the 1%.

The following is how I am going about excluding the 1%, which works, but I want to see if there is a better way of going about this:

intercept(request: HttpRequest<any>, next:HttpHandler: Observable<HttpEvent<any>> {
  let position = request.url.indexOf('api/');
  if (position > 0){
    let destination: string = request.url.substr(position + 4);
    let matchFound: boolean = false;

    for (let address of this.addressesToUse){
      if (new RegExp(address).test(destination)){
        matchFound = true;

    if (!matchFound){
      ...DO WORK to add the headers


What I wound up doing is having an array of urls (in Regex Format) that I did not want to be used in the interceptor like so:

import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs';

export class AddCustomHeadersInterceptor implements HttpInterceptor {
  urlsToNotUse: Array<string>;

  ) {

    this.urlsToNotUse= [

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    if (this.isValidRequestForInterceptor(request.url)) {
      let modifiedRequest = request.clone({
        setHeaders: {
          //DO WORK HERE

      return next.handle(modifiedRequest);
    return next.handle(request);

  private isValidRequestForInterceptor(requestUrl: string): boolean {
    let positionIndicator: string = 'api/';
    let position = requestUrl.indexOf(positionIndicator);
    if (position > 0) {
      let destination: string = requestUrl.substr(position + positionIndicator.length);
      for (let address of this.urlsToNotUse) {
        if (new RegExp(address).test(destination)) {
          return false;
    return true;