I have xhr and fetch type of xhr requests and responses that I want to intercept.
FETCH API CALLS
I've tried
window.fetch = function() {
// Intercept the request here
}
and
XMLHttpRequest.prototype.send = function() {
// Intercept the request here
}
But I want to write one generic function which intercepts all the xhr requests and responses.
By default, fetch() doesn’t provide a way to intercept requests, but it’s not hard to come up with a workaround. You can overwrite the global fetch method and define your own interceptor, like this:
fetch = (originalFetch => {
return (...arguments) => {
const result = originalFetch.apply(this, arguments);
return result.then(console.log('Request was sent'));
};
})(fetch);
fetch('https://api.github.com/orgs/axios')
.then(response => response.json())
.then(data => {
console.log(data)
});
`
I need to implement a cancel-able client-side HTTP request in Node.js, without using external libraries. I'm giving a Promise object - cancellationPromise - which gets rejected when the cancellation is externally requested. This is how I know I may need to call request.abort().
The question is, should I be calling request.abort() only if https.request is still pending and response object is not yet available?
Or, should I be calling it even if I already got the response object and am processing the response data, like in the code below? In which case, will that stop any more response.on('data') events from coming?
async simpleHttpRequest(url, oauthToken, cancellationPromise) {
let cancelled = null;
let oncancel = null;
cancellationPromise.catch(error => {
cancelled = error; oncancel && oncancel(error) });
try {
const response = await new Promise((resolve, reject) => {
const request = https.request(
url.toString(),
{
method: 'GET',
headers: { 'Authorization': `Bearer ${oauthToken}` }
},
resolve);
oncancel = error => request.abort();
request.on('error', reject);
request.end();
});
if (cancelled) throw cancelled;
// do I need "oncancel = null" here?
// or should I still allow to call request.abort() while fetching the response's data?
// oncancel = null;
try {
// read the response
const chunks = await new Promise((resolve, reject) => {
response.on('error', reject);
const chunks = [];
response.on('data', data => chunks.push(data));
response.on('end', () => resolve(chunks));
});
if (cancelled) throw cancelled;
const data = JSON.parse(chunks.join(''));
return data;
}
finally {
response.resume();
}
}
finally {
oncancel = null;
}
}
It depends what you want to achieve by aborting a request.
Just a bit of background. HTTP 1 is not able to "cancel" a request it sends it and then waits for the response. You cannot "roll back" the request you did. You need a distributed transaction to do so. (Further reading.) As the MDN developer document states:
The XMLHttpRequest.abort() method aborts the request if it has already been sent. When a request is aborted, its readyState is changed to XMLHttpRequest.UNSENT (0) and the request's status code is set to 0.
Basically you stop the response from being processed by your application. The other application will probably (if you called abort() after it was sent to it) finish its processing anyways.
From the perspective of the question:
The question is, should I be calling request.abort() only if https.request is still pending and response object is not yet available?
TL.DR.: It only matters from the point of view of your application. As I glance at your code, I think it will work fine.
Essentially when i call my function getToken() it should return the bearer + token from the api.
The problem I have is that due to the asynchronous process that happens, the data is not returned instantly; so in reading the following resource:
How do I return the response from an asynchronous call?
My understanding is that I need to return my response in the form of a promise, and set a timeout to ensure that the return accounts for the time it takes for the server to send back my request in the form of a response.
var request = require('request-promise');
var time = require('timers');
class Auth {
getToken() {
let options = {
method: 'POST',
uri: 'https://example.com/service/ep',
body: {
username: 'someUser',
password: 'somePass'
},
json: true
}
request(options)
.then(function (body) {
// console.log(body)
return new Promise((resolve) => {
time.setTimeout(() => {
resolve(body)
},3000)
});
})
.catch(function (err) {
return err
});
}
}
module.exports = new Auth
Unfortunately when i run my program in the node repel, it returns nothing and it does not appear to wait; of course when i log my response 'console.log(body)', it appears meaning there must be something wrong with how i'm returning my promise; i'm quite new to the likes of promises.
Could use with a second pair of eyes.
My understanding is that I need to return my response in the form of a promise, and set a timeout to ensure that the return accounts for the time it takes for the server to send back my request in the form of a response.
No. You need to return a promise (request already gives you one) and then the code you return the promise to needs to expect a promise (and call then() on it to get the data).
You don't need any time delays.
var request = require('request-promise');
var time = require('timers');
class Auth {
getToken() {
let options = {
method: 'POST',
uri: 'https://example.com/service/ep',
body: {
username: 'someUser',
password: 'somePass'
},
json: true
}
return request(options);
}
}
module.exports = new Auth
const auth = require("Auth");
auth.getToken().then(function (data) {
console.log(data);
});
This question already has answers here:
How do I return the response from an asynchronous call?
(41 answers)
Closed 3 months ago.
I am trying to use a Node.JS application to make and receive API requests. It does a get request to another server using Axios with data it receives from an API call it receives. The second snippet is when the script returns the data from the call in. It will actually take it and write to the console, but it won't send it back in the second API.
function axiosTest() {
axios.get(url)
.then(function (response) {
console.log(response.data);
// I need this data here ^^
return response.data;
})
.catch(function (error) {
console.log(error);
});
}
...
axiosTestResult = axiosTest();
response.json({message: "Request received!", data: axiosTestResult});
I'm aware this is wrong, I'm just trying to find a way to make it work. The only way I can seem to get data out of it is through console.log, which isn't helpful in my situation.
The issue is that the original axiosTest() function isn't returning the promise. Here's an extended explanation for clarity:
function axiosTest() {
// create a promise for the axios request
const promise = axios.get(url)
// using .then, create a new promise which extracts the data
const dataPromise = promise.then((response) => response.data)
// return it
return dataPromise
}
// now we can use that data from the outside!
axiosTest()
.then(data => {
response.json({ message: 'Request received!', data })
})
.catch(err => console.log(err))
The function can be written more succinctly:
function axiosTest() {
return axios.get(url).then(response => response.data)
}
Or with async/await:
async function axiosTest() {
const response = await axios.get(url)
return response.data
}
Guide on using promises
Info on async functions
I know this post is old. But i have seen several attempts of guys trying to answer using async and await but getting it wrong. This should clear it up for any new references
UPDATE: May 2022
This answer is still having lots of interest and have updated it to use arrow functions
const axiosTest = async () {
try {
const {data:response} = await axios.get(url) //use data destructuring to get data from the promise object
return response
}
catch (error) {
console.log(error);
}
}
you can populate the data you want with a simple callback function,
let's say we have a list named lst that we want to populate,
we have a function that pupulates pupulates list,
const lst = [];
const populateData = (data) => {lst.push(data)}
now we can pass the callback function to the function which is making the axios call and we can pupulate the list when we get data from response.
now we make our function that makes the request and pass populateData as a callback function.
function axiosTest (populateData) {
axios.get(url)
.then(function(response){
populateData(response.data);
})
.catch(function(error){
console.log(error);
});
}
The axios library creates a Promise() object. Promise is a built-in object in JavaScript ES6. When this object is instantiated using the new keyword, it takes a function as an argument. This single function in turn takes two arguments, each of which are also functions — resolve and reject.
Promises execute the client side code and, due to cool Javascript asynchronous flow, could eventually resolve one or two things, that resolution (generally considered to be a semantically equivalent to a Promise's success), or that rejection (widely considered to be an erroneous resolution). For instance, we can hold a reference to some Promise object which comprises a function that will eventually return a response object (that would be contained in the Promise object). So one way we could use such a promise is wait for the promise to resolve to some kind of response.
You might raise we don't want to be waiting seconds or so for our API to return a call! We want our UI to be able to do things while waiting for the API response. Failing that we would have a very slow user interface. So how do we handle this problem?
Well a Promise is asynchronous. In a standard implementation of engines responsible for executing Javascript code (such as Node, or the common browser) it will resolve in another process while we don't know in advance what the result of the promise will be. A usual strategy is to then send our functions (i.e. a React setState function for a class) to the promise, resolved depending on some kind of condition (dependent on our choice of library). This will result in our local Javascript objects being updated based on promise resolution. So instead of getters and setters (in traditional OOP) you can think of functions that you might send to your asynchronous methods.
I'll use Fetch in this example so you can try to understand what's going on in the promise and see if you can replicate my ideas within your axios code. Fetch is basically similar to axios without the innate JSON conversion, and has a different flow for resolving promises (which you should refer to the axios documentation to learn).
GetCache.js
const base_endpoint = BaseEndpoint + "cache/";
// Default function is going to take a selection, date, and a callback to execute.
// We're going to call the base endpoint and selection string passed to the original function.
// This will make our endpoint.
export default (selection, date, callback) => {
fetch(base_endpoint + selection + "/" + date)
// If the response is not within a 500 (according to Fetch docs) our promise object
// will _eventually_ resolve to a response.
.then(res => {
// Lets check the status of the response to make sure it's good.
if (res.status >= 400 && res.status < 600) {
throw new Error("Bad response");
}
// Let's also check the headers to make sure that the server "reckons" its serving
//up json
if (!res.headers.get("content-type").includes("application/json")) {
throw new TypeError("Response not JSON");
}
return res.json();
})
// Fulfilling these conditions lets return the data. But how do we get it out of the promise?
.then(data => {
// Using the function we passed to our original function silly! Since we've error
// handled above, we're ready to pass the response data as a callback.
callback(data);
})
// Fetch's promise will throw an error by default if the webserver returns a 500
// response (as notified by the response code in the HTTP header).
.catch(err => console.error(err));
};
Now we've written our GetCache method, lets see what it looks like to update a React component's state as an example...
Some React Component.jsx
// Make sure you import GetCache from GetCache.js!
resolveData() {
const { mySelection, date } = this.state; // We could also use props or pass to the function to acquire our selection and date.
const setData = data => {
this.setState({
data: data,
loading: false
// We could set loading to true and display a wee spinner
// while waiting for our response data,
// or rely on the local state of data being null.
});
};
GetCache("mySelelection", date, setData);
}
Ultimately, you don't "return" data as such, I mean you can but it's more idiomatic to change your way of thinking... Now we are sending data to asynchronous methods.
Happy Coding!
axiosTest() needs to return axios.get, which in turn returns a Promise.
From there, then can be used to execute a function when said Promise resolves.
See Promise for more info.
Alternatively, await can be used from within the scope of some async function.
// Dummy Url.
const url = 'https://jsonplaceholder.typicode.com/posts/1'
// Axios Test.
const axiosTest = axios.get
// Axios Test Data.
axiosTest(url).then(function(axiosTestResult) {
console.log('response.JSON:', {
message: 'Request received',
data: axiosTestResult.data
})
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.18.0/axios.js"></script>
IMO extremely important rule of thumb for your client side js code is to keep separated the data handling and ui building logic into different funcs, which is also valid for axios data fetching ... in this way your control flow and error handlings will be much more simple and easier to manage, as it could be seen from this
ok fetch
and this
NOK fetch
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<script>
function getUrlParams (){
var url_params = new URLSearchParams();
if( window.location.toString().indexOf("?") != -1) {
var href_part = window.location.search.split('?')[1]
href_part.replace(/([^=&]+)=([^&]*)/g,
function(m, key, value) {
var attr = decodeURIComponent(key)
var val = decodeURIComponent(value)
url_params.append(attr,val);
});
}
// for(var pair of url_params.entries()) { consolas.log(pair[0]+ '->'+ pair[1]); }
return url_params ;
}
function getServerData (url, urlParams ){
if ( typeof url_params == "undefined" ) { urlParams = getUrlParams() }
return axios.get(url , { params: urlParams } )
.then(response => {
return response ;
})
.catch(function(error) {
console.error ( error )
return error.response;
})
}
// Action !!!
getServerData(url , url_params)
.then( response => {
if ( response.status === 204 ) {
var warningMsg = response.statusText
console.warn ( warningMsg )
return
} else if ( response.status === 404 || response.status === 400) {
var errorMsg = response.statusText // + ": " + response.data.msg // this is my api
console.error( errorMsg )
return ;
} else {
var data = response.data
var dataType = (typeof data)
if ( dataType === 'undefined' ) {
var msg = 'unexpected error occurred while fetching data !!!'
// pass here to the ui change method the msg aka
// showMyMsg ( msg , "error")
} else {
var items = data.dat // obs this is my api aka "dat" attribute - that is whatever happens to be your json key to get the data from
// call here the ui building method
// BuildList ( items )
}
return
}
})
</script>
After 6 hours of fluttering, I realized it was a one-line problem. If you are interfering with the axios life-cycle, you may have forgotten this line:
componentDidMount() {
this.requestInterceptor = axios.interceptors.request.use((request) => {
this.updateApiCallFor(request.url, true);
return request;
});
this.responseInterceptor = axios.interceptors.response.use((response) => {
this.updateApiCallFor(response.config.url, false);
return response; // THIS LINE IS IMPORTANT !
}, (error) => {
this.updateApiCallFor(error.config.url, false);
throw error;
});
async makes a function return a Promise
await makes a function wait for a Promise
code async/await
// https://www.npmjs.com/package/axios
const axios = require('axios')
/* --- */
async function axiosTest() {
let promiseAxios = axios.get( 'https://example.com' )
/* --- */
console.log( await promiseAxios )
}
/* --- */
axiosTest()
replit.com Stackoverflow - Returning data from Axios API
replit.com Stackoverflow - How to return values from async
code async/await with return
// https://www.npmjs.com/package/axios
const axios = require('axios')
/* --- */
async function axiosTest() {
console.log( await promiseAxios() )
}
/* --- */
axiosTest()
/* --- */
// create function for promise axios and return it
function promiseAxios() {
return axios.get( 'https://example.com' )
}
replit.com Stackoverflow - Returning data from Axios API - return
replit.com Stackoverflow - How to return values from async - return
Try this,
function axiosTest() {
axios.get(url)
.then(response => response.data)
.catch(error => error);
}
async function getResponse () {
const response = await axiosTest();
console.log(response);
}
getResponse()
It works, but each function where you want to get the response needs to be an async function or use an additional .then() callback.
function axiosTest() {
axios.get(url)
.then(response => response.data)
.catch(error => error);
}
async function getResponse () {
axiosTest().then(response => {
console.log(response)
});
}
getResponse()
If anyone knows a way to avoid this please do tell.
Also checkout Katsiaryna (Kate) Lupachova's article on Dev.to. I think it will help.
async handleResponse(){
const result = await this.axiosTest();
}
async axiosTest () {
return await axios.get(url)
.then(function (response) {
console.log(response.data);
return response.data;})
.catch(function (error) {
console.log(error);
});
}
You can find check https://flaviocopes.com/axios/#post-requests url and find some relevant information in the GET section of this post.
You can use Async - Await:
async function axiosTest() {
const response = await axios.get(url);
const data = await response.json();
}
I'm trying to migrate my API calls from using jQuery ajax to using the Fetch API.
I was using jQuery ajaxStart and ajaxStop to display a loading spinner during server calls.
I'm running several parallel server requests, I want the spinner to start when the first request start and to stop when the last request settled.
It was pretty straight foward with jQuery. However, I can't find a similiar technique using the fetch API.
Any ideas ?
You can use Promise to notify when fetch is called and completed
var params = {
a: 1,
b: 2
};
var data = new FormData();
data.append("json", JSON.stringify(params));
var currentRequest = new Request("/echo/json/", {
method: "POST",
body: data
});
var start, complete;
var fetchStart = new Promise(function(_start) {
start = _start;
})
var fetchComplete = new Promise(function(_complete) {
complete = _complete;
});
// do stuff when `fetch` is called
fetchStart.then(function(startData) {
console.log(startData)
});
// do stuff when `fetch` completes
fetchComplete.then(function(completeData) {
console.log(completeData)
});
var request = fetch(currentRequest);
[request, start({
"fetchStarted": currentRequest
})].shift()
.then(function(res) {
if (res.ok) {
// resolve `fetchComplete` `Promise` when `fetch` completes
complete({
"fetchCompleted": res
})
};
return res.json();
})
.then(function(data) {
document.body.textContent = JSON.stringify(data)
})
.catch(function(err) {
// if error, pass error to `fetchComplete`
complete({
"fetchCompleted": res,
"error": err
});
});
jsfiddle https://jsfiddle.net/abbpbah4/18/
See also Fetch: POST json data
Just start your spinner before the call to fetch and stop it in the finally
state.showSpinner = true;
Promise.all([fetch(url1), fetch(url2)])
.then(success => console.log(success))
.catch(error => console.error(error))
.finally(() => state.showSpinner = false);