In the following Express function:
app.get('/user/:id', function(req, res){
res.send('user' + req.params.id);
});
What are req and res? What do they stand for, what do they mean, and what do they do?
Thanks!
req is an object containing information about the HTTP request that raised the event. In response to req, you use res to send back the desired HTTP response.
Those parameters can be named anything. You could change that code to this if it's more clear:
app.get('/user/:id', function(request, response){
response.send('user ' + request.params.id);
});
Edit:
Say you have this method:
app.get('/people.json', function(request, response) { });
The request will be an object with properties like these (just to name a few):
request.url, which will be "/people.json" when this particular action is triggered
request.method, which will be "GET" in this case, hence the app.get() call.
An array of HTTP headers in request.headers, containing items like request.headers.accept, which you can use to determine what kind of browser made the request, what sort of responses it can handle, whether or not it's able to understand HTTP compression, etc.
An array of query string parameters if there were any, in request.query (e.g. /people.json?foo=bar would result in request.query.foo containing the string "bar").
To respond to that request, you use the response object to build your response. To expand on the people.json example:
app.get('/people.json', function(request, response) {
// We want to set the content-type header so that the browser understands
// the content of the response.
response.contentType('application/json');
// Normally, the data is fetched from a database, but we can cheat:
var people = [
{ name: 'Dave', location: 'Atlanta' },
{ name: 'Santa Claus', location: 'North Pole' },
{ name: 'Man in the Moon', location: 'The Moon' }
];
// Since the request is for a JSON representation of the people, we
// should JSON serialize them. The built-in JSON.stringify() function
// does that.
var peopleJSON = JSON.stringify(people);
// Now, we can use the response object's send method to push that string
// of people JSON back to the browser in response to this request:
response.send(peopleJSON);
});
I noticed one error in Dave Ward's answer (perhaps a recent change?):
The query string paramaters are in request.query, not request.params. (See https://stackoverflow.com/a/6913287/166530 )
request.params by default is filled with the value of any "component matches" in routes, i.e.
app.get('/user/:id', function(request, response){
response.send('user ' + request.params.id);
});
and, if you have configured express to use its bodyparser (app.use(express.bodyParser());) also with POST'ed formdata. (See How to retrieve POST query parameters? )
Request and response.
To understand the req, try out console.log(req);.
Related
I'm sending a post request to a cloud function which contains the following body:
{message: "this is the message"}
If I try to print the entire body of the request, it shows it, but if I try to get the message field, I get undefined in the console.
Here's my function:
exports.myCloudFunction = functions.https.onRequest((req: any, res: any) => {
console.log(req.body)\\prints the body of the request fine
console.log(req.body.message)\\prints "undefined"
cors(req, res, () => {
const pl = req.body.message;
console.log(pl);\\prints "undefined"
});
return res.send("all done")
});
You don't need a body parser for Cloud Functions as described in the other answer here. Cloud Functions will automatically parse JSON and put the parsed JSON object in the body attribute. If you want this to happen automatically, you should set the content type of the request to "application/json" as described in the linked documentation. Then you can use req.body as you'd expect.
I personally haven't worked with firebase before, but from your code and the fact that req.body prints the body, it seems that you probably need to parse the request-body as json in order to be able to access the message property:
const body = JSON.parse(req.body);
console.log(body.message);
It could also be the case that you need to setup a bodyparser for json content. In a normal express-app you can do this using (note that you don't need the manual parsing from above anymore using bodyparser):
const bodyParser = require('body-parser');
app.use(bodyParser.json();
EDIT:
see Doug's answer for the correct way to do this, i.e. to fix your request and set the content-type to application/json in order for Cloud Functions to automatically parse and populate req.body with the request body.
You need to just convert the request body into a JSON object in cloud function.
const body = JSON.parse(req.body);
// message
console.log(body.message)
I am trying to hit the URL http://localhost:3000/analyze/imageurl=https://www.google.com/ from my browser.
However, due to the presence of //, it does not correctly hit the URL, and gives me an error message, Cannot GET /analyze/imageurl=https://www.google.com/
If I get rid of the backquotes as follows, http://localhost:3000/analyze/imageurl=httpswww.google.com/, it does work correctly.
My backend API looks like this
app.get('/analyze/:imageurl', function (req, res) {
console.log('printing image url:' + req.params.imageurl);
}
Is there a way I can pass in the imageurl with backquotes as a query parameter?
You need to encode your URL before pass it on query string, using encodeURIComponent. For example:
var urlParam = encodeURIComponent('https://www.google.com/');
console.log(urlParam); // https%3A%2F%2Fwww.google.com%2F
var url = 'http://localhost:3000/analyze/' + urlParam;
console.log(url); // http://localhost:3000/analyze/https%3A%2F%2Fwww.google.com%2F
// Decode it in API handler
console.log(decodeURIComponent(urlParam)); // https://www.google.com/
encodeURIComponent
One approach could be to use Express' req.query in your route. It would look something like this:
// Client makes a request to server
fetch('http://localhost:3000/analyze?imageurl=https://google.com')
// You are able to receive the value of specified parameter
// from req.query.<your_parameter>
app.get('/analyze', (req, res, next) => {
res.json(req.query.imageurl)
})
Нello! I am looking to call a function which has been passed to an expressRouter.post(...) call.
This expressRouter.post(...) call is occurring in a file which I am unable to modify. The code has already been distributed to many clients and there is no procedure for me to modify their versions of the file. While I have no ability to update this file for remote clients, other developers are able to. I therefore face the issue of this POST endpoint's behaviour changing in the future.
I am also dealing with performance concerns. This POST endpoint expects req.body to be a parsed JSON object, and that JSON object can be excessively large.
My goal is to write a GET endpoint which internally activates this POST endpoint. The GET endpoint will need to call the POST endpoint with a very large JSON value, which has had URL query params inserted into it. The GET's functionality should always mirror the POST's functionality, including if the POST's functionality is updated in the future. For this reason I cannot copy/paste the POST's logic. Note also that the JSON format will never change.
I understand that the issue of calling an expressjs endpoint internally has conventionally been solved by either 1) extracting the router function into an accessible scope, or 2) generating an HTTP request to localhost.
Unfortunately in my case neither of these options are viable:
I can't move the function into an accessible scope as I can't modify the source, nor can I copy-paste the function as the original version may change
Avoiding the HTTP request is a high priority due to performance considerations. The HTTP request will require serializing+deserializing an excessively large JSON body, re-visiting a number of authentication middlewares (which require waiting for further HTTP requests + database queries to complete), etc
Here is my (contrived) POST endpoint:
expressRouter.post('/my/post/endpoint', (req, res) => {
if (!req.body.hasOwnProperty('val'))
return res.status(400).send('Missing "val"');
return res.status(200).send(`Your val: ${req.body.val}`);
});
If I make a POST request to localhost:<port>/my/post/endpoint I get the expected error or response based on whether I included "val" in the JSON body.
Now, I want to have exactly the same functionality available, but via GET, and with "val" supplied in the URL instead of in any JSON body. I have attempted the following:
expressRouter.get('/my/get/endpoint/:val', (req, res) => {
// Make it seem as if "val" occurred inside the JSON body
let fakeReq = {
body: {
val: req.params.val
}
};
// Now call the POST endpoint
// Pass the fake request, and the real response
// This should enable the POST endpoint to write data to the
// response, and it will seem like THIS endpoint wrote to the
// response.
manuallyCallExpressEndpoint(expressRouter, 'POST', '/my/post/endpoint', fakeReq, res);
});
Unfortunately I don't know how to implement manuallyCallExpressEndpoint.
Is there a solution to this problem which excludes both extracting the function into an accessible scope, and generating an HTTP request?
This seems possible, but it may make more sense to modify req and pass it, rather than create a whole new fakeReq object. The thing which enables this looks to be the router.handle(req, res, next) function. I'm not sure this is the smartest way to go about this, but it will certainly avoid the large overhead of a separate http request!
app.get('/my/get/endpoint/:val', (req, res) => {
// Modify `req`, don't create a whole new `fakeReq`
req.body = {
val: req.params.val
};
manuallyCallExpressEndpoint(app, 'POST', '/my/post/endpoint', req, res);
});
let manuallyCallExpressEndpoint = (router, method, url, req, res) => {
req.method = method;
req.url = url;
router.handle(req, res, () => {});
};
How about a simple middleware?
function checkVal(req, res, next) {
const val = req.params.val || req.body.val
if (!val) {
return res.status(400).send('Missing "val"');
}
return res.status(200).send(`Your val: ${val}`);
}
app.get('/my/get/endpoint/:val', checkVal)
app.post('/my/post/endpoint', checkVal)
This code isn't tested but gives you rough idea on how you can have the same code run in both places.
The checkVal function serves as a Express handler, with request, response and next. It checks for params first then the body.
I am wondering if there is any preference in using request.body or request.params in node.js when sending data from client to server?
You can fit more (diverse) data in the body than in the url. You can pass any string (special characters) in the body, while encoding them in the url would get you vulnerable to status 414 (Request-URI Too Long). And it's a lot easier to use the body when passing arrays and complex objects :)
I would say that a best practice would be that you should use params when doing a get, but use body for post, put and patch.
a sample get
app.get "/api/items/:id", (req, res) ->
itemController.getItem req.params.id, (item, error) =>
if !error
res.send 'item': item
else
res.send 'error: error
a sample post
app.post "/api/items", (req, res) ->
itemController.saveItem req.body, (item, error) =>
if !error
res.send 'item': item
else
res.send 'error: error
You would add validation on as well, but this has been how I have been writing all of my endpoints.
It's been over 4 years since this question was asked, however, I would still chime in to make sure somebody else stumbling upon this post has more information to understand this concept better.
req.body and req.params server two different purposes.
you would use req.body when you need to send data to a server (to store it or something), like in a "POST" request to a server. For instance, check out the following:
You are doing a "POST" request to mongodb to save a blog post. In this scenario, you would want to get the data coming in the body of the request and send it to the db. Here you would use req.body
app.post("/blog", function(req, res){
var data = req.body.blog;
.... // code to send data to the db
....
});
req.params is used when you want to extract a "param" from the url. let's say you want to extract an "id" which is part of the url. For instance "id" is the number in the following url after questions
stackoverflow.com/questions/18187424/
app.get("/xyz/questions/:id", function(req, res){
var useId = req.params.id;
...
...
});
Hope, it helps.
Thanks,
Kartik
I have two situations to get data from DB
To show normal data
http://exampleapp.com/task/{{taskId}}
To edit data via posting
http://exampleapp.com/task/{{taskId}}/?state={{app.state}}
Both url have the same http://exampleapp.com/task/{{taskId}} just a little bit different with last phrase ?state={{app.state}}
I use Express routing as followed:
app.get('/task/:taskId/(?state=:status(pending|cancel|confirmed|deleted))?', routes.task.show);
But I dont know why it does not work ?
For example error: Cannot GET /task/51d2c53f329b8e0000000001 when going to h**p://exampleapp.com/task/51d2c53f329b8e0000000001
Query strings cannot be defined in routes. You access query string parameters from req.query.
app.get('/task/:taskId', function(req, res) {
if (req.query.state == 'pending') { ... }
});
However, if you're modifying a task, this is not the appropriate way to do it. GET requests SHOULD be idempotent: the request SHOULD NOT modify state. That's what POST requests are for.
app.get('/task/:taskId', function(req, res) {
// show task info based on `req.params.taskId`
});
app.post('/task/:taskId', function(req, res) {
// set task `req.params.taskId` to state `req.body.state`
});
You could either have a <form> that posts to the task, or make an ajax request:
$.post('/task/1', { state: 'pending' }, function() { ... });
According to the Express API, you cannot mix RegExp routes with string routes.
You should do something like this (I'm assuming taskId is an integer):
app.get(/^\/task/([0-9]+)/(?state=:status(pending|cancel|confirmed|deleted))?, routes.task.show);
However, I don't see why you cannot only check if req.query.state is defined in your route. It's probably less error prone and easier:
app.get("/task/:taskId", function( req, res, next ) {
if (req.query.state) {
// Do things
}
next();
});
Your problem is that query strings are not considered in routing. You will either have to redesign your urls (ie, include the state into the url itself, instead of the query string) or check the query string in your route handler function.