I have serviceWorker.js in this I am Cache the URL and REsponse data into cache storage
APi Contains the Headers but while using this below method it's getting error to fetch the data How to Pass the headers in this addall array urls .
await cache.addAll(API_URLS);
I am Using Javascript, i required Answers in javascript only.
Adv Thank You
I dont get how we use req in express. I undrstand that the server can respond back to client,but when it comes to req object im confused. Is req when the server is asking for somethong from the client?
HTTP is an application, client-server protocol. Everytime that a client want the server to perform an action, it has to make a request. The HTTP protocol defines a set of actions or verbs that are available to the client so it can make each request using one specific verb (GET, POST, PATCH, PUT, DELETE, etc). It doesn't matter what verb the client uses, only the client can initiate a comunication with the server using one of that verbs. So this is how exactly an HTTP GET request looks like:
GET / HTTP/1.1
Host: example.com
User-Agent: curl/7.69.1
Accept: */*
The first line contains the verb used, in this case GET, the path requested, in this case /, and the protocol version, in this case HTTP/1.1. The next lines, are a set of key value pairs called the headers of that request, which can define a lot of aspects of the request made by the client to the server. By the way, an HTTP server never could or will start a request to a client, a client always is the one that make the request, and the server is always the one that response that request. One of the aspects of that request for example, is the destination host, that is present in the header host with the value of example.com. Bellow of the headers, all the HTTP requests have a blank line and then the body of the request, which normally contains the data that is sent from the client to the server. In this case, no data body is sent on the request.
Express is an HTTP server based on the HTTP module available on Node.js. Express simplifies the way that the native Node.js HTTP server works. Here is tipically how an Express app looks like:
const express = require('express');
const app = express();
// This is called a router
app.get('/path', (req, res) => {
// This router will perform some action with the req object
// And will send a response to the client
});
So, on the example above, the method app.get(...), available on Express applications, allows the server to deal with the GET requests that come from the client. The app.get() method takes two arguments, a path and a callback function. The path argument represent the string that goes after the name server, for example, in the URL www.example.com/test, the hostname is www.example.com, and the path is /test. That method app.get() is also called a Router. So, the router of the example will deal with the GET requests to that server which also define /path value as the path the request is sent to. Once a request to the server fit those two conditions, that callback will be triggered.
So, finally we get to the answer. The res variable is an object (a set of key-pair values separated by commas and locked into curly braces), that contains the data of the HTTP request, into a friendly legible object. For example, if you want to print to the console the path that the client used, you can print it like this console.log(req.path), or you can get all the headers of that HTTP request, you can use console.log(req.headers). The req object is one of the 5 main objects in Express, in fact the Express documentation defines a ton of methods that you can use with the request object (req). To get deep into the request object, you can see the official Express documentation in this link. The callback defined into the router, can use the req object, to extract information of the client's request, process it and return a response to the client later.
With an express server, you get two objects passed to a request handler.
req is data about the incoming request (things that were sent from the client). It contains the headers on the request, it contains a parsed query string, it contains the URL path, it's generally the object where middleware puts things for request handlers to use. While Express adds a bit more to this object, you can see the general concept of the req object by looking and the http.IncomingMessage object documented here. This is what the object starts out as and then Express adds more to it. The express version of the object is documented here.
res is the response object. This is all about sending a response. It will hold the outbound headers you want to send with the request. It contains the methods you use for sending a response. The core object is an http.ServerResponse object documented here and then Express adds some more things to the object on top of that which is document here.
I'm doing a simple exercise where I use the Fetch API to interact with another website. The Fetch API resolves to a Response object. My next goal is to set a cookie on this Response object, but I noticed that the headers property on the Response object is read-only. Perhaps there is something very simple that I've overlooked, but how can I set a cookie in the Response object's header?
Edit: To clarify, the Response object returned by the Fetch call is what I want to return back to the client, but before I do that I want to set a cookie in the header so that the client will have a cookie saved.
In express.js, middlewares can change request object and response object. So, my question is what exactly these request object and response object are and what do they contain.
From expressjs documentation a request is:
The req object represents the HTTP request and has properties for the request query string, parameters, body, HTTP headers, and so on.
And the response:
he res object represents the HTTP response that an Express app sends when it gets an HTTP request.
Basically you use a request to know what the client is asking for.
And you use the response object to send the response data to the client.
Had the same questions when i started with express. I found a nice article, explaining my questions.
http://www.murvinlai.com/req-and-res-in-nodejs.html
UPDATE
from the page:
What is Req & Res?
Req -> Http (https) Request Object.
You can get the request query, params, body, headers and cookies from it.
You can overwrite any value or add anything there.
However, overwriting headers or cookies will not affect the output back to the browser.
Res -> Http (https) Response Object.
The response back to the client browser.
You can put new cookies value and that will write to the client browser (under cross domain rules)
Once you res.send() or res.redirect() or res.render(), you cann do it again, otherwise, there will be uncaught error.
Me too had this same doubts.
Request Object
The req object represents the HTTP request and has properties for the request query string, parameters, body, HTTP headers, and so on
Response Object
The res object represents the HTTP response that an Express app sends when it gets an HTTP request.
Reference Link
I'm trying to get the user info by using /users/:id as well as the user's group info /users/:id/groups using OKTA API and the problem is that the response is sent as a string format and I need to JSON.parse() it before using, which obviously is an extra job. Did anyone faced the same issue?
The solution was similar to the Noob Coder's comment, I've used the request middleware to make http requests, it gives you an request configuration option {json : true} which automatically
sets body but to JSON representation of value and adds Content-type: application/json header. Additionally, parses the response body as JSON.