I want to create a web component using svelte. To create a web component it's necessary to include the svelte tag option
<svelte:options tag="{"my-custom-component}"></svelte:options>
It creates a custom component with that name but doesn't work properly because we have to provide this tag for all the child components as well! I added it to all the child components but it still doesn't work, turns out I use third-party libraries and I don't know any way to have that option there!
Is there a way to create the custom components with svelte which includes third-party libraries?
You can use regular svelte components (including third party) ones inside your component.
But you'll need to compile those with different compiler settings in your rollup/webpack config.
And due to the nature of scoped styling in web components (Shadow DOM) the css won't work in these components. So it depends on the library if it still works.
You might be able to turn off scoped styling in the future:
Issue #1748: Custom element without shadow DOM
But scoped styling could have been the reason why you wanted/needed webcomponents in the first place.
This is one of those "what should we do about this"-questions. As you know, web components are supposed to be small, contained applications for websites. However, sometimes these needs to be styled depending on the site they're embedded on.
Example: "Sign up to our newsletter"-component. This component would have a few key items:
An input box
A button
Maybe recaptcha
A method that talks to your service once the button is pressed (passing in the email)
We're going to use Google and YouTube as examples. Google's color scheme is blue (let's imagine that) and YouTube's color scheme is red. The component would then be something like <newsletter-signup></newsletter-signup> on the page you're embedding it in. Both Google and YouTube have this.
The problem comes in, when the component needs to inherit the styles from Google and YouTube. A few deprecated CSS selectors would be great for this, because Google and YouTube's style sheets could simply enable colors for the Shadow DOM, so we wouldn't have to copy/paste the styles. The component should theoretically not know anything about the styles from the host, because we want it to inherit from the host (Google and YouTube).
At the moment, I'm creating a web component using Angular 6, which has a lot of styles, because it has a lot of elements. I'm copy/pasting styles, Bootstrap, icons, and so on from the host site, then styling them based on <newsletter-signup brand="google"></newsletter-signup>. So if the brand is Google, the colors should be red, for example.
This is really bad, because of a few reasons:
Styles have to be updated on both the web component and on the host
Duplicated code is never a good idea
If all the styles are copied 1:1, the amount of bytes required for styles is doubled
How would I, as a developer, take this into account? How do I make styles on the host, then apply them on my web component (call it inheritance)? I'm sure someone has had the exact same problem with Shadow DOM as I am experiencing. Thanks for reading.
I realize you do not want to write same kind of rules for your common component(selector)
i.e. you want to do styling as where your common selector is placed.
Things you can do to handle this:
1. Create your own logical css framework
Write most commonly used CSS rules in global css.For example if you have integrated bootstrap and you want to override bootstrap, you will write most common overrides in app.css which overrides bootstrap.
"styles": [
"node_modules/bootstrap/dist/css/bootstrap.min.css",
"src/styles/app.scss"
],
This app.scss should be written in way to which you can override.
Send Rules as input
send custom rules Obj and use in elements you want to override.
<newsletter [input]="customRulesObj"></newsletter>
component.ts
customRulesObj = new CustomRulesClass();
customRulesObj.color = 'red';
You can send rules in input in various component by creating a common class
as you know where you are embedding this component.
Extend this component from a common component
If you are too concerned for css you can extend your component from a common component which provides you with css logic as per need.
export class NewsLetterComponent extends CSSComponent implements OnInit
{
}
css-component.ts
In this component can logically define css as per host, current routerlink and
other multiple if else condition.
You can define rules by switch case conditions and bind those rules to component you have extended.
One of the biggest must-do's of web components is: My host (page where I'm embedding my web component) should not depend on the web component nor know about the web component.
What this basically means: Styles of my web component should not be shared with the host.
If my host decides to update the styles, it should affect my web component. Not the other way around. To solve this, I imported the external styles from my host directly inside the CSS file using #import. Here's an example:
import url("https://my-host.com/styles/core.css");
my-component {
//all styles goes here
}
I did this using SASS but can be done using regular CSS.
This is not a great solution at all, but it does what I want: Inherit the styles from the host. Although I would have to import every stylesheet there is, it still works.
A downside to my solution: When I load the page, it will send a request to the style from the <link> element inside the <head>-tag my host, but also to the style inside my import. So the styles are loaded twice. For our application, which is internal use only, it doesn't matter if we request additional ~200 KB data.
This question is a few years old and the situation has changed. The way to share styles with web components is now to use link tags to a shared stylesheet.
Inside each component:
<link rel="stylesheet" href="https://my-host.com/styles/core.css">
Reference:
https://github.com/WICG/webcomponents/issues/628
Since Angular uses view encapsulation is it possible to support multiple themes in Angular 2? I mean the user should be able to click on a button and change the color theming of the whole application.
PS: I am using Angular 4 with angular-cli with SASS support.
Currently I am able to generate static themes with a _variable.scss file which is imported in each component's sass based stylesheet.
But, my requirement is end user should be able to choose his own color theme.
Ideally in non-angular websites I would just add a new compiled css file to the <head> tag using javascript. Since shadow DOM generates separate style for each component and adds them in to the <head> how I change the style for each component dynamically?
you can try the css method var(), for more details can read this blog
I'm writing a single-page web application, but I'm struggling with some frameworks.
It seems almost every modern framework, like Bootstrap or Framework7
uses very basic classnames like row or navbar.
Because of this I can't use both frameworks on a webpage at the same time, which is limiting my options. For some pages (like a homepage) Bootstrap is nice, but for other pages I prefer the components of Framework7.
Is there any way to solve this problem, other than using entirely different HTML-files ?
The following options can be used to namespace CSS:
iframe per framework
Create a SASS file which namespaces each framework using the cascade by prefixing each framework rule with a selector which maps to a parent element with the specified class name.
References
How to namespace Twitter Bootstrap so styles don't conflict
Prevent iFrame from taking parent CSS
What is the convention when it comes to AngularJS directives and styling them?
Do I style via JS or stylesheet? How do I keep things self-contained and modular?
It depends heavily on the framework you use. In many MVC frameworks, you can write your own view helpers which automatically append a JS-file and CSS-file belonging to the same directive. Otherwise, you can use directive templates or Shadow DOM.
There is no convention as this is an issue with other libraries like extjs. However, in extjs, each component has a config to put styles in much like inline styles.
My approach is to include a separate css with the directive as it nicely separates the styling. And since angular directives allow separate template, your html is nicely separated from the javascript as well.