11/28/2023 0 Comments Comment utiliser just color pickerJavaScript class mixins are a time-tested way to share code between components. Instead of copy-pasting snippets into our element definitions, there are better ways to share code across elements. Things like handling user input, or asynchronously fetching data over the network can end up in most if not all of the components in a given project. Oftentimes when writing components, we come across a bit of logic or behaviour that repeats itself in multiple places. Now let's move on to reactivity, meaning to update our element's state-of-affairs in reaction to some input like user actions or changing properties. We covered HTML and CSS with, ShadowRoot, and :host. Tracking the Mouse with a Reactive ControllerĮvery component needs HTML, CSS, and JavaScript to handle properties, events, and reactivity. We also nod to the browser, letting it know that the background and transform properties are likely to change. This is going to come in handy in the next step when we use JavaScript to animate the loupe element. Our #loupe rule gives our colour-picking loupe a pleasing circular shape, but - crucially - defines its background-color and position in terms of CSS Custom Properties also called CSS Variables. We also threw in a cross-hair cursor and some default dimensions for good measure. The business-end of our element's :host styles is a pair of linear-gradient() calls, one which fades from transparent to grey, the other which turns 360 degrees around the colour wheel in 10% increments as it moves from the far left of our element to the far right. We can finally write simple, à la carte selectors in CSS, scoping our work to the task at hand.Įquipped with our knowledge of the Shadow DOM, let's dive into our element's styles. Now that we've learned a little more about Shadow DOM works, we can answer that question for ourselves: The Shadow DOM (supported in all browsers) removes the need for complicated css-in-js tooling or class naming conventions like BEM. If this is supposed to be a reusable component, won't those styles and IDs affect the page? Shouldn't we use BEM, or add JavaScript or a command-line tool to transform those IDs into unique random class names? Shadow DOM puts us in complete * control of our component's HTML and CSS, letting us put whatever HTML and CSS we want inside it without worrying about how they affect the rest of the page. Without shadow DOM, we should see our element in the console, but we don't. Open up color-picker.css and paste in the following. Let's change that by applying some good-old CSS. If you save the file, the dev server will reload the page, but we still won't see any changes because our element's content is invisible. Last, we call fine(), which assigns the HTML tag name to custom element class, and instructs the browser to upgrade the elements already present in the document. In the constructor, we attach a ShadowRoot to our element, then stamp the contents of the template we created into it. Next we declare our custom element class. From then on, we can create as many elements as we want, but each one will stamp a clone of the existing HTML, which is much faster than parsing it again. By using a, we make sure the browser does the work of parsing our HTML only one time, when the page loads. We'll add a link to our component's private CSS and two nested elements that we'll use later on to enhance our component. We start by declaring a element to hold our element's HTML. To catch up on what web components are, check out my blog series:Įnter fullscreen mode Exit fullscreen mode If you've ever written a component with one of the popular JS frameworks, you're good to go. You should also be familiar with the concept of component-based UI design and have an idea of what a web component is. You don't need to be an expert, but you should have the basics covered. Object-oriented programming for web developers and the JavaScript class keyword.How to use the DOM API to query for elements.To get the most out of this article, you should have a comfortable understanding of HTML, CSS, and JavaScript including: Adding Controller Support to our Element.Tracking the Mouse with a Reactive Controller.Fires a Custom Event when the user clicks or drags.Updates it's Shadow DOM via a small class mixin.Tracks the mouse position using a Reactive Controller.Displays a colour spectrum using CSS Gradients.In the end, we'll have a custom element that: Let's build a colour picker web component using HTML, CSS, and a little bit of JavaScript.
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