Angular2 appear warning XMLHttpRequest at chrome - rest

Question

I used Http Restful API at Angular2, but appear the following warning message.
Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
Please tell me how to do that.
http_restful_service.ts
import { Injectable } from '#angular/core';
import { Http, Headers, Response } from '#angular/http';
import { Observable } from 'rxjs/Observable';
#Injectable()
export class HTTPRestfulService {
constructor(private _http: Http) {}
getAllProjectName() {
var headers = new Headers();
headers.append('Content-Type','charset=uft-8');
return
this._http.get('http://localhost/api/database/',
{headers: headers})
.map(res => res.json());
}
}
backstage_view.component.ts
import { Component, OnInit } from '#angular/core';
import { HTTPRestfulService } from './../../../service/http_restful_service';
#Component({
moduleId: module.id,
selector: 'backstage_view',
templateUrl: './backstage_view.component.html',
styleUrls: ['./backstage_view.component.css']
})
export class BackstageViewComponent implements OnInit {
allProjects: string;
constructor(private _restfulapi: HTTPRestfulService) {}
ngOnInit() {
this._restfulapi.getAllProjectName()
.subscribe(
data => this.allProjects = data,
error => console.log(error),
);
}
}

Answer 1

Why can't you pass the content-type as 'application/json' format,
let url= `http://localhost/api/database/`;
let headers = new Headers();
headers.append('Content-Type','application/json');
let params = new URLSearchParams;
params.append('id', id);
params.append('user_id', user_id);
return this.authHttp.post( url, { headers:headers, search:params })
.map(res => res.json());