Inline CSS styles in React: how to implement a:hover?

Question

I think onMouseEnter and onMouseLeave are the ways to go, but I don't see the need for an additional wrapper component. Here is how I implemented it:

var Link = React.createClass({
  getInitialState: function(){
    return {hover: false}
  },
  toggleHover: function(){
    this.setState({hover: !this.state.hover})
  },
  render: function() {
    var linkStyle;
    if (this.state.hover) {
      linkStyle = {backgroundColor: 'red'}
    } else {
      linkStyle = {backgroundColor: 'blue'}
    }
    return(
      <div>
        <a style={linkStyle} onMouseEnter={this.toggleHover} onMouseLeave={this.toggleHover}>Link</a>
      </div>
    )
}

You can then use the state of hover (true/false) to change the style of the link.

Late to party but come with solution. You can use "&" to defines styles for hover nth Child etc:

day: {
    display: "flex",
    flex: "1",
    justifyContent: "center",
    alignItems: "center",
    width: "50px",
    height: "50px",
    transition: "all 0.2s",
    borderLeft: "solid 1px #cccccc",

    "&:hover": {
      background: "#efefef"
    },
    "&:last-child": {
      borderRight: "solid 1px #cccccc"
    }
},

I'm in the same situation. Really like the pattern of keeping the styling in the components but the hover states seems like the last hurdle.

What I did was writing a mixin that you can add to your component that needs hover states. This mixin will add a new hovered property to the state of your component. It will be set to true if the user hovers over the main DOM node of the component and sets it back to false if the users leaves the element.

Now in your component render function you can do something like:

<button style={m(
     this.styles.container,
     this.state.hovered && this.styles.hover,
)}>{this.props.children}</button>

Now each time the state of the hovered state changes the component will rerender.

I've also create a sandbox repo for this that I use to test some of these patterns myself. Check it out if you want to see an example of my implementation.

https://github.com/Sitebase/cssinjs/tree/feature-interaction-mixin

You can use Radium - it is an open source tool for inline styles with ReactJS. It adds exactly the selectors you need. Very popular, check it out - Radium on npm

Here's my solution using React Hooks. It combines the spread operator and the ternary operator.

style.js

export default {
  normal:{
    background: 'purple',
    color: '#ffffff'
  },
  hover: {
    background: 'red'
  }
}

Button.js

import React, {useState} from 'react';
import style from './style.js'

function Button(){

  const [hover, setHover] = useState(false);

  return(
    <button
      onMouseEnter={()=>{
        setHover(true);
      }}
      onMouseLeave={()=>{
        setHover(false);
      }}
      style={{
        ...style.normal,
        ...(hover ? style.hover : null)
      }}>

        MyButtonText

    </button>
  )
}

Full CSS support is exactly the reason this huge amount of CSSinJS libraries, to do this efficiently, you need to generate actual CSS, not inline styles. Also inline styles are much slower in react in a bigger system. Disclaimer - I maintain JSS.