Day 70: the defined pseudo-class
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It’s time to get me up to speed with modern CSS. There’s so much new in CSS that I know too little about. To change that I’ve started #100DaysOfMoreOrLessModernCSS. Why more or less modern CSS? Because some topics will be about cutting-edge features, while other stuff has been around for quite a while already, but I just have little to no experience with it.
:defined
represents any element that has been defined. This includes standard elements and custom elements that have been successfully defined.
:defined {
background-color: #000;
color: #fff;
}
Standard elements
<p>I'm defined</p>
<small>I'm defined</small>
I'm defined
I'm definedUndefined custom elements
<unde-fined>I'm not defined</unde-fined>
Defined custom elements
<de-fined>I'm defined</de-fined>
class BasicComponent extends HTMLElement {
constructor() {
super();
}
}
customElements.define('de-fined', BasicComponent);
Deprecated elements
<center>test</center>
<font>test</font>
<blink>test</blink>
Further reading
Do you want to learn even more awesome CSS?
I'm running a workshop with my friends at Smashing Magazine in which I introduce you to the most useful modern features in CSS and show how you can implement them today in your code base to improve scalability, maintainability, and productivity.
Learn more about the workshop!
Overview: 100 Days Of More Or Less Modern CSS