I'm trying to split out a "prebid" file , so as I can have seperate files from the "bidders", analytics client, bidder settings and some other bits. I've basically made my original file the main.js and have split out some of the code into different files such as
var pbjs = pbjs || {};
pbjs.que = pbjs.que || [];
pbjs.que.push(function() {
pbjs.addAdUnits(adUnits);
requirejs(['bidder_settings']);
requirejs(['pbjs_config']);
pbjs.requestBids({
bidsBackHandler: initAdserver,
timeout: PREBID_TIMEOUT
});
});
i'm trying to call in the files within the orginal file, so as it pulls those bits in, it sometimes works but other times it doesnt seem to load certain bits, any clue what i'm doing wrong/ is there a way to make sure the file loads the "modules/ seperate file" in sequencence down the page?
This sounds like an asynchronous race condition on your page where requirejs is not loading your modules by the time Prebid needs them to finish the auction. According to the [requirejs docs] (https://requirejs.org/docs/api.html#jsfiles) you should be using a callback to then run code that will require your loaded modules.
example:
var pbjs = pbjs || {};
pbjs.que = pbjs.que || [];
requirejs(['bidder_settings', 'pbjs_config', ],
function (bidder_settings, pbjs_config) {
pbjs.que.push(function () {
pbjs.addAdUnits(adUnits);
requirejs(['bidder_settings']);
requirejs(['pbjs_config']);
// do what you need with modules here
pbjs.requestBids({
bidsBackHandler: initAdserver, // make sure you utilize disableInitialLoad
timeout: PREBID_TIMEOUT
});
});
}
);
Related
I apologise for the phrasing of the question - it's a bit difficult to sum up as a question - please feel free to edit it if you can clarify. Also, as this quite a complex and long query - thank you to all those who are putting in the time to read through it!
I have 4 files (listed with directory tree from project root) as part of a project I'm building which aims to scrape blockchains and take advantage of multiple cores do get the job done:
./main.js
./scraper.js
./api/api.js
./api/litecoin_api.js
main.js
const { scraper } = require('./scraper.js')
const blockchainCli = process.env.BLOCKSCRAPECLI || 'litecoin-cli'
const client = (args) => {
// create child process which returns a promise which resolves after
// data has finished buffering from locally hosted node using cli
let child = spawn(`${blockchainCli} ${args.join(' ')}`, {
shell: true
})
// ... wrap command in a promise here, etc
}
const main = () => {
// count cores, spawn a worker per core using node cluster, add
// message handlers, then begin scraping blockchain with each core...
scraper(blockHeight)
}
main()
module.exports = {
client,
blockchainCli
}
scraper.js
const api = require('./api/api.js')
const scraper = async (blockHeight) => {
try {
let blockHash = await api.getBlockHashByHeight(blockHeight)
let block = await api.getBlock(blockHash)
// ... etc, scraper tested and working, writes to shared writeStream
}
module.exports = {
scraper
}
api.js
const { client, blockchainCli } = require('../main.js')
const litecoin = require('./litecoin_api')
let blockchain = undefined
if (blockchainCli === 'litecoin-cli' || blockchainCli === 'bitcoin-cli') {
blockchain = litecoin
}
// PROBLEM HERE: blockchainCli (and client) are both undefined if and
// only if running scraper from main.js (but not if running scraper
// from scraper.js)
const decodeRawTransaction = (txHash) => {
return client([blockchain.decodeRawTransaction, txHash])
}
const getBlock = (blockhash) => {
return client([blockchain.getBlock, blockhash])
}
const getBlockHashByHeight = (height) => {
return client([blockchain.getBlockHash, height])
}
const getInfo = () => {
return client([blockchain.getInfo])
}
const getRawTransaction = (txHash, verbose = true) => {
return client([blockchain.getRawTransaction, txHash, verbose])
}
module.exports = {
decodeRawTransaction,
getBlock,
getBlockHashByHeight,
getInfo,
getRawTransaction
}
So, I've taken out most the noise in the files which I don't think is necessary but it's open source so if you need more take a look here.
The problem is that, if I start the scraper from inside scraper.js by doing, say, something like this: scraper(1234567) it works like a charm and outputs the expected data to a csv file.
However if I start the scraper from inside the main.js file, I get this error:
Cannot read property 'getBlockHash' of undefined
at Object.getBlockHashByHeight (/home/grayedfox/github/blockscrape/api/api.js:19:29)
at scraper (/home/grayedfox/github/blockscrape/scraper.js:53:31)
at Worker.messageHandler (/home/grayedfox/github/blockscrape/main.js:81:5)
I don't know why, when launching the scraper from main.js, the blockchain is undefined. I thought it might be from the destructuring, but removing the curly braces from around the first line in the example main.js file doesn't change anything (same error).
Things are a bit messy at the moment (in the middle of developing this branch) - but the essential problem now is that it's not clear to me why the require would fail (cannot see variables inside main.js) if it's used in the following way:
main.js (execute scraper()) > scraper.js > api.js
But not fail (can see variables inside main.js) if it's run like this:
scraper.js (execute scraper()) > api.js
Thank you very much for your time!
You have a circular dependency between main and api, each requiring in the other. main requires api through scraper and api directly requires main. That causes things not to work.
You have to remove the circular dependency by putting common shared code into its own module that can be included by both, but doesn't include others that include it. It just needs better modularity.
I'm trying to create a small web app and I have a question about module.exports
supppose I have a file counter.js
var counter = 0;
module.exports = {
add: function() {
counter++;
},
get: function() {
return counter;
}
}
and I try to reference this file in several files suppose app.js and count.js all located in the same directory
// from app.js
var a = require('./counter.js');
a.add();
console.log(a.get()); // the value is 1
// from count.js
var b = require('./counter.js');
b.add();
console.log(b.get()); // the value is 2?
will the value be 1 or 2?
The result will be 2
From nodejs.org doc
Modules are cached after the first time they are loaded. This means (among other things) that every call to require('foo') will get exactly the same object returned, if it would resolve to the same file.
Multiple calls to require('foo') may not cause the module code to be executed multiple times. This is an important feature. With it, "partially done" objects can be returned, thus allowing transitive dependencies to be loaded even when they would cause cycles.
If you mean that (for example) app.js will include count.js via require() or that both app.js and count.js will be included by a third file via require(), then they all share an instance and the answer is 2.
If you mean what happens if you run node app.js and then run node count.js, then in that case, every file gets its own instance of the required module, so it will be 1.
i am working on a project in which a nodejs program calls another program in a separate file.
this is how i've added the two:
var ocr = require('./index.js'); //this imports the file
var arr = ocr.ocr_pan(); //this calls the function in that file
am not sure but I guess the problem is that the process resumes before ocr.ocr_pan() returns the result and var arr becomes undefined.
or there is some problem in returning the result from ocr.ocr_pan()
I simply use return.
and I have also tried this : How to return array from module in NodeJS
didn't work
what more can be done?
Assuming that this file is the same directory as index.js file, code in index.js should be something like this:
// Write your function
var ocr_pan = function() {
// Do whatever you like
return result;
};
// Export it, make publicly visible to other files
module.exports = {
ocr_pan: ocr_pan
};
Using Express with Node.js, we might do something like this:
app.use('api/:controller/:action/:id', function(req,res,next){
var controller = req.params.controller;
var action = req.params.action;
var route = require('./routes/' + controller + '/' + action);
route(req,res,next);
}
now this is all fine and well, except there is at least one problem: the route file is dynamically loaded at runtime if this file has not been 'require'd yet. Which means it's a little bit slower at least.
Does someone have a script that recurses through a directory and pre-loads/pre-requires all the .js files when a server first starts up?
I have a similar problem for the front-end as well, using RequireJS. The solution seems to be to write a bash script that writes out all the .js filepaths in a directory and its subdirectories to a text file. then when the server starts up, it reads that text file and requires all the files in the directory that are listed in the text file. Is that the best way to do it?
If you can use io.js, it can preload modules using command-line -r or --require:
iojs -r <module_name> server.js
I created an NPM module that does this for the front-end, doing it for Node.js / CommonJS is another story.
https://www.npmjs.com/package/requirejs-metagen
you can use it like so:
var grm = require('requirejs-metagen'); //you can use with Gulp
var controllersOpts = {
inputFolder: './public/static/app/js/controllers/all',
appendThisToDependencies: 'app/js/controllers/',
appendThisToReturnedItems: '',
eliminateSharedFolder: true,
output: './public/static/app/js/meta/allControllers.js'
};
grm(controllersOpts,function(err){
//handle errors your own way
});
it generates a corresponding AMD/RequireJS module like so:
define(
[
"app/js/controllers/all/jobs",
"app/js/controllers/all/users"
],
function(){
return {
"jobs": arguments[0],
"users": arguments[1]
}
});
you can also require subdirectories and all that stuff like so:
var allViewsOpts = {
inputFolder: './public/static/app/js/jsx',
appendThisToDependencies: 'app/js/',
appendThisToReturnedItems: '',
eliminateSharedFolder: true,
output: './public/static/app/js/meta/allViews.js'
}
grm(allViewsOpts );
which generates output like so:
define([
"app/js/jsx/BaseView",
"app/js/jsx/reactComponents/FluxCart",
"app/js/jsx/reactComponents/FluxCartApp",
"app/js/jsx/reactComponents/FluxProduct",
"app/js/jsx/reactComponents/Item",
"app/js/jsx/reactComponents/Job",
"app/js/jsx/reactComponents/JobsList",
"app/js/jsx/reactComponents/listView",
"app/js/jsx/reactComponents/Picture",
"app/js/jsx/reactComponents/PictureList",
"app/js/jsx/reactComponents/RealTimeSearchView",
"app/js/jsx/reactComponents/Service",
"app/js/jsx/reactComponents/ServiceChooser",
"app/js/jsx/reactComponents/todoList",
"app/js/jsx/relViews/getAll/getAll",
"app/js/jsx/relViews/jobs/jobsView",
"app/js/jsx/standardViews/dashboardView",
"app/js/jsx/standardViews/overviewView",
"app/js/jsx/standardViews/pictureView",
"app/js/jsx/standardViews/portalView",
"app/js/jsx/standardViews/registeredUsersView",
"app/js/jsx/standardViews/userProfileView"
],
function(){
return {
"BaseView": arguments[0],
"reactComponents/FluxCart": arguments[1],
"reactComponents/FluxCartApp": arguments[2],
"reactComponents/FluxProduct": arguments[3],
"reactComponents/Item": arguments[4],
"reactComponents/Job": arguments[5],
"reactComponents/JobsList": arguments[6],
"reactComponents/listView": arguments[7],
"reactComponents/Picture": arguments[9],
"reactComponents/PictureList": arguments[10],
"reactComponents/RealTimeSearchView": arguments[11],
"reactComponents/Service": arguments[12],
"reactComponents/ServiceChooser": arguments[13],
"relViews/getAll/getAll": arguments[14],
"relViews/jobs/jobsView": arguments[15],
"standardViews/dashboardView": arguments[16],
"standardViews/overviewView": arguments[17],
"standardViews/pictureView": arguments[18],
"standardViews/portalView": arguments[19],
"standardViews/registeredUsersView": arguments[20],
"standardViews/userProfileView": arguments[21]
}
});
I need to update the library so it returns the stream so you can handle when it completes, otherwise it works great.
maybe this question is a little silly, but is it possible to load multiple .js files with one require statement? like this:
var mylib = require('./lib/mylibfiles');
and use:
mylib.foo(); //return "hello from one"
mylib.bar(): //return "hello from two"
And in the folder mylibfiles will have two files:
One.js
exports.foo= function(){return "hello from one";}
Two.js
exports.bar= function(){return "hello from two";}
I was thinking to put a package.json in the folder that say to load all the files, but I don't know how. Other aproach that I was thinking is to have a index.js that exports everything again but I will be duplicating work.
Thanks!!
P.D: I'm working with nodejs v0.611 on a windows 7 machine
First of all using require does not duplicate anything. It loads the module and it caches it, so calling require again will get it from memory (thus you can modify module at fly without interacting with its source code - this is sometimes desirable, for example when you want to store db connection inside module).
Also package.json does not load anything and does not interact with your app at all. It is only used for npm.
Now you cannot require multiple modules at once. For example what will happen if both One.js and Two.js have defined function with the same name?? There are more problems.
But what you can do, is to write additional file, say modules.js with the following content
module.exports = {
one : require('./one.js'),
two : require('./two.js'),
/* some other modules you want */
}
and then you can simply use
var modules = require('./modules.js');
modules.one.foo();
modules.two.bar();
I have a snippet of code that requires more than one module, but it doesn't clump them together as your post suggests. However, that can be overcome with a trick that I found.
function requireMany () {
return Array.prototype.slice.call(arguments).map(function (value) {
try {
return require(value)
}
catch (event) {
return console.log(event)
}
})
}
And you use it as such
requireMany("fs", "socket.io", "path")
Which will return
[ fs {}, socketio {}, path {} ]
If a module is not found, an error will be sent to the console. It won't break the programme. The error will be shown in the array as undefined. The array will not be shorter because one of the modules failed to load.
Then you can bind those each of those array elements to a variable name, like so:
var [fs, socketio, path] = requireMany("fs", "socket.io", "path")
It essentially works like an object, but assigns the keys and their values to the global namespace. So, in your case, you could do:
var [foo, bar] = requireMany("./foo.js", "./bar.js")
foo() //return "hello from one"
bar() //return "hello from two"
And if you do want it to break the programme on error, just use this modified version, which is smaller
function requireMany () {
return Array.prototype.slice.call(arguments).map(require)
}
Yes, you may require a folder as a module, according to the node docs. Let's say you want to require() a folder called ./mypack/.
Inside ./mypack/, create a package.json file with the name of the folder and a main javascript file with the same name, inside a ./lib/ directory.
{
"name" : "mypack",
"main" : "./lib/mypack.js"
}
Now you can use require('./mypack') and node will load ./mypack/lib/mypack.js.
However if you do not include this package.json file, it may still work. Without the file, node will attempt to load ./mypack/index.js, or if that's not there, ./mypack/index.node.
My understanding is that this could be beneficial if you have split your program into many javascript files but do not want to concatenate them for deployment.
You can use destructuring assignment to map an array of exported modules from require statements in one line:
const requires = (...modules) => modules.map(module => require(module));
const [fs, path] = requires('fs', 'path');
I was doing something similar to what #freakish suggests in his answer with a project where I've a list of test scripts that are pulled into a Puppeteer + Jest testing setup. My test files follow the naming convention testname1.js - testnameN.js and I was able use a generator function to require N number of files from the particular directory with the approach below:
const fs = require('fs');
const path = require('path');
module.exports = class FilesInDirectory {
constructor(directory) {
this.fid = fs.readdirSync(path.resolve(directory));
this.requiredFiles = (this.fid.map((fileId) => {
let resolvedPath = path.resolve(directory, fileId);
return require(resolvedPath);
})).filter(file => !!file);
}
printRetrievedFiles() {
console.log(this.requiredFiles);
}
nextFileGenerator() {
const parent = this;
const fidLength = parent.requiredFiles.length;
function* iterate(index) {
while (index < fidLength) {
yield parent.requiredFiles[index++];
}
}
return iterate(0);
}
}
Then use like so:
//Use in test
const FilesInDirectory = require('./utilities/getfilesindirectory');
const StepsCollection = new FilesInDirectory('./test-steps');
const StepsGenerator = StepsCollection.nextFileGenerator();
//Assuming we're in an async function
await StepsGenerator.next().value.FUNCTION_REQUIRED_FROM_FILE(someArg);