import {HttpClientModule} from '@angular/common/http';
imports: [
 BrowserModule,
 HttpClientModule
]

import {HttpClient} from "@angular/common/http";
constructor(public http:HttpClient) { }

var api = "http://a.itying.com/api/productlist";
this.http.get(api).subscribe(response => {
 console.log(response);
});

import {HttpClient,HttpHeaders} from "@angular/common/http";
constructor(public http:HttpClient) { }

const httpOptions = {
 headers: new HttpHeaders({ 'Content-Type': 'application/json' })
};
var api = "http://127.0.0.1:3000/doLogin";
this.http.post(api,{username:'張三',age:'20'},httpOptions).subscribe(response => {
 console.log(response);
});

import {HttpClientModule,HttpClientJsonpModule} from
'@angular/common/http';
imports: [
 BrowserModule,
 HttpClientModule,
 HttpClientJsonpModule
]

import {HttpClient} from "@angular/common/http";
constructor(public http:HttpClient) { }

var api = "http://a.itying.com/api/productlist";
this.http.jsonp(api,'callback').subscribe(response => {
console.log(response);
});

cnpm install axios --save

import axios from 'axios';
axios.get('/user?ID=12345')
.then(function (response) {
// handle success
console.log(response);
})
.catch(function (error) {
// handle error
console.log(error);
})
.then(function () {
// always executed
});

import { Injectable } from '@angular/core';
import axios from 'axios';
@Injectable({
 providedIn: 'root'
})
export class HttpserviceService {
 constructor() { }
 axiosGet(api){
   return new Promise((resolve,reject)=>{
    axios.get(api)
     .then(function (response) {
      // handle success   
      resolve(response)
     });
  })

 } 
}