When multiple declarations have the same key name, each one overrides the last. This can be a problem with object literal syntax, especially when the property value needs to be prefixed. As of today (9/6/2016), there is no built-in solution for this issue.
To address this problem without adding a build step and staying in the CSS-in-JS realm, I created a simple package called Style It, which allows you to write CSS easily.
npm install style-it --save
Functional Syntax (JSFIDDLE)
import React from 'react';
import Style from 'style-it';
class Intro extends React.Component {
render() {
return Style.it(`
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: -webkit-box;
display: -moz-box;
display: -ms-flexbox;
display: -webkit-flex;
display: flex;
-webkit-flex-flow: row wrap;
justify-content: space-around;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin-top: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
}
`,
<ul class="flex-container">
<li class="flex-item">1</li>
<li class="flex-item">2</li>
<li class="flex-item">3</li>
<li class="flex-item">4</li>
<li class="flex-item">5</li>
<li class="flex-item">6</li>
</ul>
);
}
}
export default Intro;
JSX Syntax (JSFIDDLE)
import React from 'react';
import Style from 'style-it';
class Intro extends React.Component {
render() {
return (
<Style>
{`
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: -webkit-box;
display: -moz-box;
display: -ms-flexbox;
display: -webkit-flex;
display: flex;
-webkit-flex-flow: row wrap;
justify-content: space-around;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin-top: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
}
`}
<ul class="flex-container">
<li class="flex-item">1</li>
<li class="flex-item">2</li>
<li class="flex-item">3</li>
<li class="flex-item">4</li>
<li class="flex-item">5</li>
<li class="flex-item">6</li>
</ul>
</Style>
}
}
export default Intro;
The HTML / CSS code is derived from Chris Coyier's article on A Complete Guide to Flexbox.