Node walk presents an API with a few events like this.
walker.on('file', (root, filestats, next) => {
// next should be called to goto next file
next();
});
walker.on('end', () => {
// the end of the stream
});
Is it reactive if from the subscriber you're calling a function to inform the source to go to the next item in the stream ? Events don't wait for the subscriber to react to it, right ?
How do I transform this into a Rx Observable ?
Your best bet is to create a wrapper around it:
Rx.Observable.fromWalk = function(root, options, scheduler) {
scheduler = scheduler || Rx.Scheduler.currentThread;
return Rx.Observable.create(function(observer) {
var walker = walk.walk(root, options);
function fileHandler(x) {
observer.onNext({stats : x.stats, root : x.root});
scheduler.scheduleWithState(x, function(s, i) {
i.next();
});
}
var files = Rx.Observable.fromEvent(walker, 'file',
function(arr) {
return { root : arr[0], stats : arr[1], next : arr[2] };
});
var ended = Rx.Observable.fromEvent(walker, 'end');
return new Rx.CompositeDisposable(
files.subscribe(fileHandler),
ended.subscribe(observer.onCompleted.bind(observer))
);
});
};
I updated your example accordingly
Try Rx.Observable.fromCallback:
var walkerOn = Rx.Observable.fromCallback(walker.on, walker)
var source = walkerOn('file');
var subscription = source.subscribe(observer);
Related
I'm not sure what's going on here. I have set up an API route in NextJS that returns before the data has been loaded. Can anyone point out any error here please?
I have this function that calls the data from makeRequest():
export async function getVendors() {
const vendors = await makeRequest(`Vendor.json`);
console.log({ vendors });
return vendors;
}
Then the route: /api/vendors.js
export default async (req, res) => {
const response = await getVendors();
return res.json(response);
};
And this is the makeRequest function:
const makeRequest = async (url) => {
// Get Auth Header
const axiosConfig = await getHeader();
// Intercept Rate Limited API Errors & Retry
api.interceptors.response.use(
function (response) {
return response;
},
async function (error) {
await new Promise(function (res) {
setTimeout(function () {
res();
}, 2000);
});
const originalRequest = error.config;
if (error.response.status === 401 && !originalRequest._retry) {
token[n] = null;
originalRequest._retry = true;
const refreshedHeader = await getHeader();
api.defaults.headers = refreshedHeader;
originalRequest.headers = refreshedHeader;
return Promise.resolve(api(originalRequest));
}
return Promise.reject(error);
}
);
// Call paginated API and return number of requests needed.
const getQueryCount = await api.get(url, axiosConfig).catch((error) => {
throw error;
});
const totalItems = parseInt(getQueryCount.data['#attributes'].count);
const queriesNeeded = Math.ceil(totalItems / 100);
// Loop through paginated API and push data to dataToReturn
const dataToReturn = [];
for (let i = 0; i < queriesNeeded; i++) {
setTimeout(async () => {
try {
const res = await api.get(`${url}?offset=${i * 100}`, axiosConfig);
console.log(`adding items ${i * 100} through ${(i + 1) * 100}`);
const { data } = res;
const arrayName = Object.keys(data)[1];
const selectedData = await data[arrayName];
selectedData.map((item) => {
dataToReturn.push(item);
});
if (i + 1 === queriesNeeded) {
console.log(dataToReturn);
return dataToReturn;
}
} catch (error) {
console.error(error);
}
}, 3000 * i);
}
};
The issue that I'm having is that getVendors() is returned before makeRequest() has finished getting the data.
Looks like your issue stems from your use of setTimeout. You're trying to return the data from inside the setTimeout call, and this won't work for a few reasons. So in this answer, I'll go over why I think it's not working as well as a potential solution for you.
setTimeout and the event loop
Take a look at this code snippet, what do you think will happen?
console.log('start')
setTimeout(() => console.log('timeout'), 1000)
console.log('end')
When you use setTimeout, the inner code is pulled out of the current event loop to run later. That's why end is logged before the timeout.
So when you use setTimeout to return the data, the function has already ended before the code inside the timeout even starts.
If you're new to the event loop, here's a really great talk: https://youtu.be/cCOL7MC4Pl0
returning inside setTimeout
However, there's another fundamental problem here. And it's that data returned inside of the setTimeout is the return value of the setTimeout function, not your parent function. Try running this, what do you think will happen?
const foo = () => {
setTimeout(() => {
return 'foo timeout'
}, 1000)
}
const bar = () => {
setTimeout(() => {
return 'bar timeout'
}, 1000)
return 'bar'
}
console.log(foo())
console.log(bar())
This is a result of a) the event loop mentioned above, and b) inside of the setTimeout, you're creating a new function with a new scope.
The solution
If you really need the setTimeout at the end, use a Promise. With a Promise, you can use the resolve parameter to resolve the outer promise from within the setTimeout.
const foo = () => {
return new Promise((resolve) => {
setTimeout(() => resolve('foo'), 1000)
})
}
const wrapper = async () => {
const returnedValue = await foo()
console.log(returnedValue)
}
wrapper()
Quick note
Since you're calling the setTimeout inside of an async function, you will likely want to move the setTimeout into it's own function. Otherwise, you are returning a nested promise.
// don't do this
const foo = async () => {
return new Promise((resolve) => resolve(true))
}
// because then the result is a promise
const result = await foo()
const trueResult = await result()
I have code like this:
loadImageFile(url: string, progressCallback: (progress: number) => void): Observable<string> {
return new Observable<string>(observer => {
const xhr = new XMLHttpRequest();
const nativeWindow = this.windowRef.nativeWindow;
let notifiedNotComputable = false;
xhr.open("GET", url, true);
xhr.responseType = "arraybuffer";
xhr.onprogress = event => {
if (event.lengthComputable) {
const progress: number = (event.loaded / event.total) * 100;
progressCallback(progress);
} else {
if (!notifiedNotComputable) {
notifiedNotComputable = true;
progressCallback(-1);
}
}
};
xhr.onloadend = function() {
if (!xhr.status.toString().match(/^2/)) {
// Here I want that the user of the Observable created at the top with
// "return new Observable" can use "pipe(catchError(...))".
}
if (!notifiedNotComputable) {
progressCallback(100);
}
const options: any = {};
const headers = xhr.getAllResponseHeaders();
const m = headers.match(/^Content-Type:\s*(.*?)$/im);
if (m && m[1]) {
options.type = m[1];
}
const blob = new Blob([this.response], options);
observer.next((nativeWindow as any).URL.createObjectURL(blob));
observer.complete();
};
xhr.send();
});
}
How can I make the xhr.onloadend act so the Observable returned by this loadImageFile method will throwError?
I believe my issue is that I am already inside new Observable, while it's the main function loadImageFile that should return throwError.
How can I overcome this?
PS: Please ignore this text: StackOverflow won't let me post this because it's mostly code, but in this case, I believe it makes sense, so I'm just writing this paragraph here to make the post validation pass :)
Thanks!
Here's the solution:
observer.error(xhr)
How can I check until an element is clickable using nightwatch js? I want to click on an element but when I run nightwatch, selenium does not click on the element because it is not clickable yet.
Something like this should work. Let me know if you have questions
var util = require('util');
var events = require('events');
/*
* This custom command allows us to locate an HTML element on the page and then wait until the element is both visible
* and does not have a "disabled" state. It rechecks the element state every 500ms until either it evaluates to true or
* it reaches maxTimeInMilliseconds (which fails the test). Nightwatch uses the Node.js EventEmitter pattern to handle
* asynchronous code so this command is also an EventEmitter.
*/
function WaitUntilElementIsClickable() {
events.EventEmitter.call(this);
this.startTimeInMilliseconds = null;
}
util.inherits(WaitUntilElementIsClickable, events.EventEmitter);
WaitUntilElementIsClickable.prototype.command = function (element, timeoutInMilliseconds) {
this.startTimeInMilliseconds = new Date().getTime();
var self = this;
var message;
if (typeof timeoutInMilliseconds !== 'number') {
timeoutInMilliseconds = this.api.globals.waitForConditionTimeout;
}
this.check(element, function (result, loadedTimeInMilliseconds) {
if (result) {
message = '#' + element + ' was clickable after ' + (loadedTimeInMilliseconds - self.startTimeInMilliseconds) + ' ms.';
} else {
message = '#' + element + ' was still not clickable after ' + timeoutInMilliseconds + ' ms.';
}
self.client.assertion(result, 'not visible or disabled', 'visible and not disabled', message, true);
self.emit('complete');
}, timeoutInMilliseconds);
return this;
};
WaitUntilElementIsClickable.prototype.check = function (element, callback, maxTimeInMilliseconds) {
var self = this;
var promises =[];
promises.push(new Promise(function(resolve) {
self.api.isVisible(element, function(result) {
resolve(result.status === 0 && result.value === true);
});
}));
promises.push(new Promise(function(resolve) {
self.api.getAttribute(element, 'disabled', function (result) {
resolve(result.status === 0 && result.value === null);
});
}));
Promise.all(promises)
.then(function(results) {
var now = new Date().getTime();
const visibleAndNotDisabled = !!results[0] && !!results[1];
if (visibleAndNotDisabled) {
callback(true, now);
} else if (now - self.startTimeInMilliseconds < maxTimeInMilliseconds) {
setTimeout(function () {
self.check(element, callback, maxTimeInMilliseconds);
}, 500);
} else {
callback(false);
}
})
.catch(function(error) {
setTimeout(function () {
self.check(element, callback, maxTimeInMilliseconds);
}, 500);
});
};
module.exports = WaitUntilElementIsClickable;
Add this code as a file to your commands folder. It should be called waitUntilElementIsClickable.js or whatever you want your command to be.
Usage is:
browser.waitUntilElementIsClickable('.some.css');
You can also use page elements:
var page = browser.page.somePage();
page.waitUntilElementIsClickable('#someElement');
You can use waitForElementVisible() combined with the :enabled CSS pseudo-class.
For example, the following will wait up to 10 seconds for #element to become enabled, then click it (note that the test will fail if the element doesn't become enabled after 10 seconds):
browser
.waitForElementVisible('#element:enabled', 10000)
.click('#element');
Can you show an example element,usually there should be an attribute name "disabled" if the button is not clickable, this should work.
browser.assert.attributeEquals(yourCSS, 'disabled', true)
I'm unable to comment but there are a couple of issues with the code suggested by Alex R.
First, the code will not work with Firefox as geckodriver does not return a 'status'. So this:
resolve(result.status === 0 && result.value === true)
needs to be changed to this:
resolve(result.value === true).
Second, the line:
self.client.assertion(result, 'not visible or disabled', 'visible and not disabled', message, true);
doesn't work and needs to be commented out in
order to get the code to run.
Hopefully the code below communicates the problem clearly. The issue is that in the module which uses the get method of fetchData, the value being returned is the actual Promise, rather than the JSON as desired. Any thoughts on this?
// fetchData.js module
var _ = require('lodash');
function get() {
var endpoint1 = `/endpoint1`;
var endpoint2 = `/endpoint2`;
return fetch(endpoint1)
.then((endpoint1Response) => {
return endpoint1Response.json()
.then((endpoint1JSON) => {
return fetch(endpoint2)
.then((endpoint2Response) => {
return endpoint2Response.json()
.then((endpoint2JSON) => {
var data = _.merge({}, {json1: endpoint1JSON}, {json2: endpoint2JSON});
console.log('data in fetch', data); // this logs the json
return data;
});
});
});
});
}
exports.get = get;
// module which uses get method of fetchData get
var fetchData = require('fetchData');
var data = fetchData.get();
console.log('returned from fetchData', data); // this logs a Promise
Yes, that's exactly what's supposed to happen. The whole point of promises is that their result value is not immediately available and that doesn't change just because you're obtaining one from a separate module.
You can access the value like this:
var fetchData = require('fetchData');
fetchData.get().then(data =>
console.log('returned from fetchData', data);
);
Also note that you are using promises in a non-idiomatic way and creating a "tower of doom." This is much easier on the eyes and accomplishes the same thing:
function fetchJson(endpoint) {
return fetch(endpoint)
.then(endpointResponse => endpointResponse.json());
}
function get() {
var endpoint1 = `/endpoint1`;
var endpoint2 = `/endpoint2`;
return Promise.all([fetchJson(endpoint1), fetchJson(endpoint2)])
.then(responses => {
var data = { json1: responses[0], json2: responses[1] };
console.log('data in fetch', data); // this logs the json
return data;
});
}
Edit I haven't used async/await in JavaScript, but to answer your question, I presume this would work:
async function fetchJson(endpoint) {
var res = await fetch(endpoint);
return res.json();
}
async function get() {
var endpoint1 = `/endpoint1`;
var endpoint2 = `/endpoint2`;
var data = {
json1: await fetchJson(endpoint1),
json2: await fetchJson(endpoint2)
};
console.log('data in fetch', data); // this logs the json
return data;
}
// module which uses get method of fetchData get
async function main() {
var fetchData = require('fetchData');
var data = await fetchData.get();
console.log('returned from fetchData', data);
}
return main();
I've created extension that makes some JSON request & send it to some receiver.
My problem is:
Open popup window
After it closing, extensions sends 1 request
Open it on the same page again, and extension will send 2 requests
Open again, 4 requests
Open again, 8 requests
In each uses of popup, extension will be duplicate outgoing data in geometric progression.
Why that happens?
From the panel I'm send addnewurl to the port:
AddDialog.port.on("addnewurl", function (data) {
{
AddDialog is my popup
here It handle port messages aftre popup is closed(hidded)
}
var http = require("sdk/request").Request;
var req = CreateRequest("add_url", {});
req.params = {...};
var sreq = encodeURIComponent(JSON.stringify(req));
count += 1; //Global counter, u will see it in video
console.log('count = '+count);
var cfg = {
url : getRequestURL(),
contentType : "text/html",
content : sreq,
onComplete : function (response) {
var data = {
code : response.status,
body : response.json
};
AddDialog.port.emit("addnewurldone", data);
}
};
http(cfg).post();
});
For more sense I've created a AVI video record of that. See it here:
https://dl.dropboxusercontent.com/u/86175609/Project002.avi
1.6 MB
How to resolve that?
ADDED by request more info
That function emit addnewurl:
function AddNewURL() {
var node = $("#Tree").dynatree("getActiveNode");
if (node == null) {
$("#ServerStatus").text(LocalizedStr.Status_NoGroupSelected);
$("#ServerStatus").css("color", "red");
return;
};
var nkey = node.data.key;
var aImg = null;
var data = {
ownerId : nkey,
name : $("#LinkTitle").val(),
description : $("#LinkDesc").val(),
url : $("#CurrentURL").val(),
scrcapt:$("#ScrCaptureCB :selected").val()
};
$("#load").css("display", "inline");
$("#ServerStatus").text(LocalizedStr.Status_AddURL);
self.port.emit("addnewurl", data);
};
and it calls by button:
self.port.on("showme", function onShow(data) {
....
document.querySelector('#BtnOk').addEventListener('click', function () {
AddNewURL();
});
...
});
"swomme" goes from here(main.js):
AddDialog.on("show", function () {
count = 0;
AddDialog.port.emit("showme", locTbl);
});
function addToolbarButton() {
var enumerator = mediator.getEnumerator("navigator:browser");
while (enumerator.hasMoreElements()) {
var document = enumerator.getNext().document;
var navBar = document.getElementById('nav-bar');
if (!navBar) {
return;
}
var btn = document.createElement('toolbarbutton');
btn.setAttribute('id', cBtnId);
btn.setAttribute('type', 'button');
btn.setAttribute('class', 'FLAToolButton');
btn.setAttribute('image', data.url('icons/Add.png'));
btn.setAttribute('orient', 'horizontal');
btn.setAttribute('label', loc("Main_ContextMenu"));
btn.addEventListener('click', function () {
AddDialog.show();
}, false)
navBar.appendChild(btn);
}
}
I think the problem is here
document.querySelector('#BtnOk').addEventListener('click', function () {
AddNewURL();
});
If you are running AddDialog.port.emit("showme", locTbl); when you click your toolbar button then you're adding a click listener to #BtnOk every time as well.
On the first toolbar click it will have one click listener, on the second click two, and so on. You should remove the above code from that function and only run it once.