Ionic 2 : Get the header of a response in http req

Question

I want to have some information about the response when I request an API with http in Ionic 2 / Angular 2. Informations like : response time, response size ... ect.

I use this code :

let url : "[myUrl]";
this.http.get(url).map(res => res.json()).subscribe(res => {
    console.log(res);
});

I want to get the response header.

Someone know how to do that ? :)

Answer 1

this.http.get(url).map(res => {
    console.log(res.headers); // Print http header
    return res.json();
}).subscribe(res => {
    console.log(res);
});

Angular Http request returns an Observable which contains all the information the server has passed. So you can access headers from the response as res.headers. To obtain the size of the response body you can use,

res.headers.get('Content-Length')

assuming this is present in the headers. So it depends on the information the response carries rather not what angular provides.

Response time information depends on what exactly you are looking for. For server response time in node.js you can use this package. Then in response , response time can be obtained with

res.headers.get('X-Response-Time')

If you want the total response time (including the network delay ) you will have use JavaScript timer and find the time difference between request and response.

So the information you are looking for mainly relies on the server response rather than angular. And beware of CORS in browser ( Access-Control-Expose-Headers in response header ) . You can understand more about headers here. Hope it helps.

Answer 2

You can. In the map function you can get the all the information regarding HTTP call. You can do whatever you want with the result (I've added only a console.log)

this.http.get(url).map(res => {
    console.log(res); // Print http details
    return res.json();
}).subscribe(res => {
    console.log(res);
});