I'm currently looking for a way to capture only svelte components on the DOM tree during development mode. I can see that we I run npm run dev all elements and conponents have the "class='svelte-somerandomID'". Does this only happen in development mode?
Yes, it's only in during development that all elements get a scoping class -- and only with some tools. Actually it's a hack we've added in vite-plugin-svelte to enable more power CSS only HMR.
The classes you're referring to are what Svelte uses to make the CSS in a component apply only to the elements of this component. It adds a class that is unique to the component to all elements that can be affected by the component's CSS, and it also modifies your CSS rules to add the same class to them.
Normally the compiler only adds the scoping class to elements that can actually be targeted by the existing CSS rules in your component. If you really want all the elements in a component to have the scoping class, you can use the same trick that I linked to above: add the following rule to your component's CSS.
* {}
By default the generated class names are a hash of the component's CSS content. But you can also customize them with the cssHash compiler option. Note that vite-plugin-svelte also changes how the class names are generated, to be based on the file name instead of the content.
Since every element in the component would be targeted by this roule, this will cause the Svelte compiler to add the scoping class to all the elements.
If you wanted to automatically generalize this to every element of every component, you may want to do it with a preprocessor (if you need some inspiration, the code I've linked too actually implement this with a preprocessor).
I'm not sure if this is what you really want though. For one thing, only elements get a scoping class: components don't get a scoping class, because components don't have dedicated elements in the DOM (only the ones you may or may not add via the component's markup). The above trick would only give you a mean to select every element of a Svelte component. There might probably be easier or cleaner ways to achieve what you really want. For example, a simple wrapping component, or an action, that would use wrappingElement.querySelectorAll('*') or something...
The link [https://ccamel.github.io/playground-binding.scala/index.html#playground-binding.scala/home]
has few demos of binding.scala
I have used DomListner extension in chrome to understand the dom events.
I found for each interaction there are hundreds of DOM events fired.
For example one click on calculator button results in 114 events.
It this a performance issue ?
Does binding.scala library need performance improvements ?
Does the code written using binding.scala need optimization ?
It's the expected behavior, because the DEMO that you mentioned recreated anchor elements, explicitly.
According to the Scaladoc for bind method:
Each time the value changes, in the current #dom method, all code after the current bind expression will be re-evaluated
As a result, the calc.bind call at here forces recreating the anchor element.
I created a pull request to change the class attribute instead, by avoiding the calc.bind call before XHTML literals.
Ive noted on the beta version of Material UI (https://material-ui-1dab0.firebaseapp.com/api/app-bar/) you can access the Paper properties via App Bar component. Its not obvious to me how this is done and so far my attempts have come up short.
Could someone share a working example or just a code snippet? That would be super helpful! Thanks.
As you can see in the source the AppBar component is just a glorified Paper.
If you look at how props are treated you’ll notice the ...other part. That extracts all properties that are not explicitly destructured. This is a ES feature not yet in spec but pretty solid and more or less safe to use, it’s called Object rest/spread.
Those rest object is then used to pass additional properties to the Paper component with a JSX Spread operator { ...other }.
So for example
<AppBar tabIndex={2} />
since tabIndex is not explicitly extracted during destructuring in the AppBar source it will be part of other, and therefore “passed down” to <Paper ... />.
In the react docs, they claim:
ReactElements are not to be confused with DOM Elements. A ReactElement
is a light, stateless, immutable, virtual representation of a DOM
Element.
Does this imply that a regular DOM element can be mutated? And if so, can you give an example of how you can mutate a DOM element, but the same code applied to a ReactElement would not mutate it?
I think you may be reading too deep into that statement. I believe by the word immutable, the ReactJS documentation is saying that "this will not change between the moment we define to the moment that we use it".
I believe this comes from other frameworks such as old version of ASP.NET that changed the DOM object ID and changed other aspects of the DOM element created between the moment of creation and the moment of usage in the DOM.
However, this element can still be modified once it is actually rendered onto the DOM as a regular HTML element by jQuery. The beauty and downside to the DOM is that once anything is placed into the DOM, the validity of that data cannot be trusted. At the end of the day, it's just a document. Hopefully, that helps.
React components can be modified by props or state. State is internal to the component. Props are passed from the parent component. Any mutations on DOM should be made via props or state changes. Though some jQuery code works with React, it is highly discouraged.
After more research, I think this has to do with the virtual DOM.
The virtual DOM is all about "diffing" to find the differences (if any) among its ReactElements. If ReactElements could be mutated, then the virtual DOM wouldn't need to diff, as the element would just mutate itself and that would be the current state of the virtual DOM. But the virtual DOM wants to diff, so rather than updating the existing ReactElement, what happens is you pass the virtual DOM a new version of that ReactElement. And updating itself to the most recent version (sort of like git I guess), the virtual DOM then updates the real DOM with the most recent version of itself.
The full flow looks something like this (I think)
React takes your stateful ReactComponent (i.e. it can be mutated), turns it into a statless ReactElement(s) (i.e. if something changes, it issues a new ReactElement rather than updating the old one), which are used to create your virtual DOM. If state changes in your ReactComponent, a new version of the corresponding ReactElements are created and sent to the virtual DOM. The virtual DOM runs the new version of the ReactElements against the old, updates itself, and then updates the real DOM.
Traditionally, with regular DOM elements and regular DOM, there is no diff occurring (and so you don't have two versions of DOM elements, new and old, you just have the one single version that you are mutating as you go). So instead of sending a new version of the DOM element to be diffed, you just update the existing DOM element.
further reading:
React Elements vs React Components vs Component Backing Instances
I've been working with ExtJS for a good few months now, but still don't have a perfectly clear map of what's going on behind the scenes there. I'm just talking about the building blocks of the framework and their most basic functionality.
Ext.Component
Ext.Element
DOM.Element
DOM.Node (?)
CompositeElement (?)
Whatever else (?)
For each of the abovementioned I would like to know:
How to select: by ID, by class, via parent, find (OR children OR query OR select? WTF), siblings, ComponentQuery, DOM-query, CSS-query, etc..
How to manipulate in the tree: create, append, prepend, insert after this sibling, move to that parent, remove, destroy, etc..
How to manipulate on the screen: show, hide, fade, slide, move up, down, change size, etc..
How to identify related to each other: find DOM.Element knowing its Ext.Component, find Ext.Component knowing its DOM.Element, etc..
What is the dependency between them: what happens to the DOM.Element if its Ext.Component is hidden / destroyed / changed / moved, what happens to the Ext.Component if its Ext.Element is hidden / destroyed / changed / moved, etc.
I'm looking for a methodical and logically clear layout of how each is supposed to be used and is expected to behave. I am also hoping that the described functionality can be grouped in corresponding categories, e.g. would be nice to see complement traversing methods .up() and .down() next to each other, rather than alphabetically pages apart. Of course links and examples (which the official documentation lacks so badly) are also welcome!
You can find out a whole lot about the building blocks of ExtJS (known as Ext Core) from the manual for this: http://docs.sencha.com/core/manual/. I will try to add some knowledge and highlight some key points, but you should definitely read through that for a very informative overview.
Ext.Component
The building block for the OOP paradigm within ExtJS. Essentially, this is an Object that contains inherited functionality to serve as the basis for a specialized component that will be transformed by the framework into DOM elements that are shown as HTML.
The Sencha documentation is excellent for this. Here are a couple good places to start:
http://docs.sencha.com/extjs/4.2.1/#!/guide/layouts_and_containers
http://docs.sencha.com/extjs/4.2.1/#!/guide/components
Ext.Element vs DOM Element
As an JavaScript develop knows, a DOM element is just a JS object that represents a tag in the document's HTML. Essentially, Ext.Element is a wrapper object for a DOM element that allows for ExtJS to manipulate the object. Any DOM element on the page can be wrapped as an Ext.Element to allow for this additional functionality.
For example, take this HTML tag:
<div id="myDiv">My content</div>
You can access this using
var el = document.getElementById('myDiv')
and use the basic, built-in JavaScript DOM functionality on el. You could also access this using
var el = Ext.get('myDiv')
and have a whole additional set of functionality available to apply to that element using the ExtJS library
The Sencha docs are also excellent for this. See all the available functionality for Ext.Element here: http://docs.sencha.com/extjs/4.2.1/#!/api/Ext.dom.Element
Misc
You can get an Ext.Element from a component using the getEl() method:
var myComponent = Ext.create('Ext.Component', { html: 'my component' });
var el = myComponent.getEl();
You would rarely need to go the other way, to determine a component from a DOM element. There isn't much of a use case there unless you are really hacking something. A major reason for using a framework like ExtJS is to prevent needing to do something like this; if should develop entirely within the JavaScript, you should be able to avoid having a reference to a DOM element where you need to get its containing ExtJS component.
Niklas answered pretty well about how to select components and elements. The only things I would really add is that you can use up() and down() to select relative to a component. In this way, you should use itemId on components rather than the global identifier id (using id can cause difficult-to-debug errors if you are reusing components with the same ID).
Also, to add to Niklas's answer about showing/hiding components, the framework does indeed add some CSS to the component's element, depending on what the hideMode for the component is. Learn more about that property here: http://docs.sencha.com/extjs/4.2.1/#!/api/Ext.AbstractComponent-cfg-hideMode
An excellent way to learn more is to look through all of the examples that come packaged with the framework. Open the examples in your browser, then look through the code to find out how things are done. You will find it way easier to learn this way, rather than reading it on paper or a website. Nothing beats experience when it comes to learning something new.
How to select: by ID, by class, via parent, find (OR children OR query OR select? WTF), siblings, ComponentQuery, DOM-query, CSS-query, etc..
Ext.ComponentQuery.query("*") // get all
Ext.ComponentQuery.query("button") // all buttons
Ext.ComponentQuery.query("#myid") // all controls / components myid
Ext.ComponentQuery.query("#myid", rootelement) // all controls / components myid with rootelement
Ext.ComponentQuery.query("#myid,button") // all buttons or controls / components myid
How to manipulate in the tree: create, append, prepend, insert after this sibling, move to that parent, remove, destroy, etc..
Adding button to a View:
Ext.ComponentQuery.query("#viewId")[0].add(new Ext.Button({ text: 'test'}));
There is also insert, remove and so on depending on the control you are querying.
How to manipulate on the screen: show, hide, fade, slide, move up, down, change size, etc..
Ext.ComponentQuery.query("button").forEach(function(button){ button.hide(); }) // hide all buttons
There is also show, disable, enable and so on depending on the control you are querying.
How to identify related to each other: find DOM.Element knowing its Ext.Component, find Ext.Component knowing its DOM.Element, etc..
Finding Ext.Component knowing its Dom.Element is pretty easy, you just take the ID from the DOM element and use Ext.ComponentQuery.query("#id").
There is also Ext.select('#id') for getting the object from an ID.
With the element property you can get the DOM:
var dom = Ext.ComponentQuery.query("button")[0].element.dom // Getting the DOM from the first button
var dom2 = component.element.dom // does also work as long as component is a valid sencha touch component
What is the dependency between them: what happens to the DOM.Element if its Ext.Component is hidden / destroyed / changed / moved, what happens to the Ext.Component if its Ext.Element is hidden / destroyed / changed / moved, etc.
I think, I'm not sure, that if you call .hide for instance there will be some CSS applied to the DOM for example: display: none. Internally they can use some framework like jQuery for that or the old school version document.getElementById('id').css and so one. If you call .show, it may change to display: block or whatever type it was before(this could be saved in the Sencha Touch class).
I don't know what happens if the DOM element gets destroyed. Probably the element too and then the garbage collector has some work to do.
If there are any more questions / something was unclear or not enough, don't hesitate to ask.
An attempt to answer the question myself.
Since there is no TABLE markup support on this website, I put my answer in this shared Spreadsheet. Note the comments on mouse rollover.
It's just a pattern for now. It needs work to get more legible and complete. Feel free to comment, or ask me if you would like to edit it.