In React, some packages allow you to import Components using either individual assignment: import Card from "#material-ui/core/Card", or via object destructuring: import { Card } from "#material-ui/core".
I read in a Blog that using the object destructuring syntax can have performance ramifications if your environment doesn't have proper tree-shaking functionality. The result being that every component of #material-ui/core is imported, not just the one you wanted.
In what situations could using object destructuring imports cause a decline in application performance and how serious would the impact be? Also, in an environment that does have all the bells and whistles, like the default create-react-app configuration, will using one over the other make any difference at all?
Relying on package internal structure is often discouraged but it's officially valid in Material UI:
import Card from '#material-ui/core/Card';
In order to not depend on this and keep imports shorter, top-level exports can be used
import { Card } from "#material-ui/core"
Both are interchangeable, as long as the setup supports tree-shaking. In case unused top-level exports can be tree-shaken, the second option is preferable. Otherwise the the first option is preferable, it guarantees unused package imports to not be included into the bundle.
create-react-app uses Webpack configuration that supports tree-shaking and can benefit from the second option.
Loading in extra code, such as numerous components from material-ui you may not need, has two primary performance impacts: Download time, and execution time.
Download time is simple: Your JS file(s) are larger, therefore take longer to download, especially over slower connections such as mobile. Properly slimming down your JS using mechanisms like tree shaking is always a good idea.
Execution time is a little less apparent, but also has a similar effect, this time to browsers with less computing power available - again, primarily mobile. Even if the components are never used, the browser must still parse and execute the source and pull it into memory. On your desktop with a powerful processor and plenty of memory you'll probably never notice the difference, but on a slower/older computer or mobile device you may notice a small lag even after the file(s) finish downloading as they are processed.
Assuming your build tooling has properly working tree shaking, my opinion is generally they are roughly equivalent. The build tool will not include the unused components into the compiled JS, so it shouldn't impact either download or execution time.
Related
I've written PWA application, application isn't big, but now my app.js has 800 lines of the code. It has many methods. How to move these methods to another files divided thematically?
require doesn't work
You have a few options depending on what browsers you support.
You may be able to use native support for modules. You can find more information about this in https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules This would be one of the simpler solutions as it does not require any additional tooling but at this time the support outside chrome is not very good.
A second alternative is to break up your code into multiple JS files and just load them all separately. This can have performance implications but if your files are small and few it wont cause too many problems. Just ensure that the code produced in these files put themselves onto a name object to avoid conflicts.
Ex file
(function() {
window.mycode = {};
window.mycode.func = function() {...};
})();
A third option is to use an existing module loader in the browser such as https://requirejs.org/
The fourth option, which is probably the most common, is to integrate a build step into your code that uses npm and a module loader such as webpack or browserify. This also lets you integrate babel which is really common among large javascript projects. The downside is it adds a step to your deployment that needs to be run and you need to learn how to use tools like webpack(which is surprisingly complicated). However, if you do javascript dev you will need to be familiar with them eventually.
I really like the way NodeJS (and it's browser-side counterparts) handle modules:
var $ = require('jquery');
var config = require('./config.json');
module.exports = function(){};
module.exports = {...}
I am actually rather disappointed by the ES2015 'import' spec which is very similar to the majority of languages.
Out of curiosity, I decided to look for other languages which implement or even support a similar export/import style, but to no avail.
Perhaps I'm missing something, or more likely, my Google Foo isn't up to scratch, but it would be really interesting to see which other languages work in a similar way.
Has anyone come across similar systems?
Or maybe someone can even provide reasons that it isn't used all that often.
It is nearly impossible to properly compare these features. One can only compare their implementation in specific languages. I collected my experience mostly with the language Java and nodejs.
I observed these differences:
You can use require for more than just making other modules available to your module. For example, you can use it to parse a JSON file.
You can use require everywhere in your code, while import is only available at the top of a file.
require actually executes the required module (if it was not yet executed), while import has a more declarative nature. This might not be true for all languages, but it is a tendency.
require can load private dependencies from sub directories, while import often uses one global namespace for all the code. Again, this is also not true in general, but merely a tendency.
Responsibilities
As you can see, the require method has multiple responsibilities: declaring module dependencies and reading data. This is better separated with the import approach, since import is supposed to only handle module dependencies. I guess, what you like about being able to use the require method for reading JSON is, that it provides a really easy interface to the programmer. I agree that it is nice to have this kind of easy JSON reading interface, however there is no need to mix it with the module dependency mechanism. There can just be another method, for example readJson(). This would separate the concerns, so the require method would only be needed for declaring module dependencies.
Location in the Code
Now, that we only use require for module dependencies, it is a bad practice to use it anywhere else than at the top of your module. It just makes it hard to see the module dependencies when you use it everywhere in your code. This is why you can use the import statement only on top of your code.
I don't see the point where import creates a global variable. It merely creates a consistent identifier for each dependency, which is limited to the current file. As I said above, I recommend doing the same with the require method by using it only at the top of the file. It really helps to increase the readability of the code.
How it works
Executing code when loading a module can also be a problem, especially in big programs. You might run into a loop where one module transitively requires itself. This can be really hard to resolve. To my knowledge, nodejs handles this situation like so: When A requires B and B requires A and you start by requiring A, then:
the module system remembers that it currently loads A
it executes the code in A
it remembers that is currently loads B
it executes the code in B
it tries to load A, but A is already loading
A is not yet finished loading
it returns the half loaded A to B
B does not expect A to be half loaded
This might be a problem. Now, one can argue that cyclic dependencies should really be avoided and I agree with this. However, cyclic dependencies should only be avoided between separate components of a program. Classes in a component often have cyclic dependencies. Now, the module system can be used for both abstraction layers: Classes and Components. This might be an issue.
Next, the require approach often leads to singleton modules, which cannot be used multiple times in the same program, because they store global state. However, this is not really the fault of the system but the programmers fault how uses the system in the wrong way. Still, my observation is that the require approach misleads especially new programmers to do this.
Dependency Management
The dependency management that underlays the different approaches is indeed an interesting point. For example Java still misses a proper module system in the current version. Again, it is announced for the next version, but who knows whether this will ever become true. Currently, you can only get modules using OSGi, which is far from easy to use.
The dependency management underlaying nodejs is very powerful. However, it is also not perfect. For example non-private dependencies, which are dependencies that are exposed via the modules API, are always a problem. However, this is a common problem for dependency management so it is not limited to nodejs.
Conclusion
I guess both are not that bad, since each is used successfully. However, in my opinion, import has some objective advantages over require, like the separation of responsibilities. It follows that import can be restricted to the top of the code, which means there is only one place to search for module dependencies. Also, import might be a better fit for compiled languages, since these do not need to execute code to load code.
From a performance/maintenance point of view, is it better to write my custom modules with netsuite all as one big JS, or multiple segmented script files.
If you compare it with a server side javascript language, say - Node.js the most popular, every module is written into separate file.
I generally take the approach of Object oriented javascript and put each class in a separate file which helps to organise the code.
One of the approach you can take is in development keep separate files and finally merge all files using js minifier tool like Google closure compiler when you deploy your code for production usage which can give you best of both worlds, if you are really bothered about every nano/mini seconds of performance.
If you see SuiteScript 2.0 architecture, it encourages module architecture which is easier to manage as load only those modules that you need, and it is easier to maintain multiple code files i.e. one per module considering future enhancements, bug fixes and code reuse.
Performance can never be judge by the line count of your module. We generally maintain modules for maintaining the readability and simplicity of the code. It is a good practice to put all generic functionalities in to an Utility script and use it as a library across all the modules. Again it depends on your code logic and programming style. So if you want to create multiple segments of your js file for more readability I dont think its a bad idea.
I tried fay-jquery and the included sample test.hs file results in whooping 150 kb of js file.
Even with closure compiling it is still 20 kb.
I understand that it must carry a runtime, stdlib and jquery wrappers with it.
I can tell fay not to generate stdlib (--no-stdlib and --no-builtins flags).
But i do not know how to tell it not to include jquery code.
So my question is, how can i split those static parts into a separate js file and only generate module specific code?
This way large parts of code will be loaded only once (and cached) and i can create many smaller js files for separate web pages.
Yes it's safe to split modules up, as of Fay 0.16 all modules can exist standalone (before that you could still have the runtime and fay-base separate). There are some flags for this, --print-runtime and --no-stdlib. Compile with optimizations (-O, this increases the output size, but closure will be able to minimize it even better).
Also remember that the web server should gzip this. That brings the code size down to 4.5kiB. That's pretty decent, right?
You might want to consider putting all of your javascript in one file, that means a slower initial load but then users will have it cached for future page loads.
The reason the file size is so big is that fay-jquery has a lot of FFI bindings which produce a lot of transcoding information. I think fay-jquery could be optimized a lot here to for instance use Ptr JQuery rather than just JQuery in the types, or by figuring out that a lot of this is unnecessary while compiling, or abstracting the conversions more in the compiler's output.
Another possible issue I realized a couple of days ago is that the output is now in the global scope rather than in a closure, which might mean that google closure can't remove redundant code as well as previously (haven't had time to investigate this yet). The modules generation should perhaps be changed to produce a closure for each module.
Also see Reducing output size on the wiki.
I read many times that YUI will load modules dynamically based on need. or based on parent module. Like here it is written
The overlay module will pull in the widget, widget-stack,
widget-position, widget-position-align, widget-position-constrain and
widget-stdmod extensions it uses.
So, how can I determine the final size of data getting downloaded for a web page due to YUI usage.
Actually I was thinking how one can compare the datasize of YUI with that of another library (JQuery).
If you want file size vs functionality comparison, a close approximation based on features would be the simpleyui.js package (though the feature compilation is not 1:1), and be sure to look at gzip size as Tivac said.
Also keep in mind that JS lib file size comparison used as a reason to choose one over another is often a red herring. Your site likely includes a number of images, many of which will easy be larger than the lib and several additional modules. More relevant comparisons would be how the library is structured, what its relative strengths are, what's included out of the box (officially supported features vs 3rd party plugins), its community and documentation, etc. Pretty much any lib will serve your basic DHTML needs, and neither you or your users will notice the difference. Choose what works for you, and helps you build clean, maintainable code that you or your successor won't hate in a few months.
The Configurator will give you a file-size breakdown & automatically selects the needed modules.