An Angular interceptor to parse string dates (ISO8601 format) from server response to JS Date Object. There are both RxJs 5 and RxJs 6 versions

AngularRxJs5DateHttpInterceptor.ts

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

@Injectable()
export class AngularDateHttpInterceptor implements HttpInterceptor {
  // Migrated from AngularJS https://raw.githubusercontent.com/Ins87/angular-date-interceptor/master/src/angular-date-interceptor.js
  iso8601 = /^\d{4}-\d\d-\d\dT\d\d:\d\d:\d\d(\.\d+)?(([+-]\d\d:\d\d)|Z)?$/;

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req).do((event: HttpEvent<any>) => {
      if (event instanceof HttpResponse) {
        const body = event.body;
        this.convertToDate(body);
      }
    }, (err: any) => {
      if (err instanceof HttpErrorResponse) {
        if (err.status === 401) {
        }
      }
    });
  }

  convertToDate(body) {
    if (body === null || body === undefined) {
      return body;
    }

    if (typeof body !== 'object') {
      return body;
    }

    for (const key of Object.keys(body)) {
      const value = body[key];
      if (this.isIso8601(value)) {
        body[key] = new Date(value);
      } else if (typeof value === 'object') {
        this.convertToDate(value);
      }
    }
  }

  isIso8601(value) {
    if (value === null || value === undefined) {
      return false;
    }

    return this.iso8601.test(value);
  }
}

AngularRxJs6DateHttpInterceptor.ts

import {
    HttpRequest,
    HttpHandler,
    HttpEvent,
    HttpInterceptor,
    HttpErrorResponse,
    HttpResponse
} from '@angular/common/http';
import { Observable } from 'rxjs';
import { tap } from 'rxjs/operators';

export class AngularDateHttpInterceptor implements HttpInterceptor {
    // Migrated from AngularJS https://raw.githubusercontent.com/Ins87/angular-date-interceptor/master/src/angular-date-interceptor.js
    iso8601 = /^\d{4}-\d\d-\d\dT\d\d:\d\d:\d\d(\.\d+)?(([+-]\d\d:\d\d)|Z)?$/;

    public intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        return next.handle(req).pipe(
            tap((event: HttpEvent<any>) => {
                if (event instanceof HttpResponse) {
                    const body = event.body;
                    this.convertToDate(body);
                }
            }, (err: any) => {
                if (err instanceof HttpErrorResponse) {
                    if (err.status === 401) {
                    }
                }
            }),
        );
    }

    convertToDate(body) {
        if (body === null || body === undefined) {
            return body;
        }

        if (typeof body !== 'object') {
            return body;
        }

        for (const key of Object.keys(body)) {
            const value = body[key];
            if (this.isIso8601(value)) {
                body[key] = new Date(value);
            } else if (typeof value === 'object') {
                this.convertToDate(value);
            }
        }
    }

    isIso8601(value) {
        if (value === null || value === undefined) {
            return false;
        }

        return this.iso8601.test(value);
    }
}

I have refactored by making it "type-safe", useful for those using strict typescript mode
Here is the code: https://gist.github.com/aml360/7e8efc275b0adb46bd5bb1b555b42467

For those, like me, who are using Java backends, there's one thing to be aware: the regex used works with LocalDateTime but if any DTO uses LocalDate, those fields won't be converted. I added another regex in order for them to be intercepted aswell.

Glad I found your code but I have one issue on my end. I'm using SpringBoot in the middle tier. How do I have my web service send a ISO8601 format string date in the JSON output? Right now its coming across as a number. I do want keep the field in the pojo as a java.util.Date class.