react.dev/tips/06-style-props-value-px.md

id	title	layout	permalink	prev	next
style-props-value-px	Shorthand for Specifying Pixel Values in style props	tips	style-props-value-px.html	maximum-number-of-jsx-root-nodes.html	children-props-type.html

When specifying a pixel value for your inline style prop, React automatically appends the string "px" for you after your number value, so this works:

/** @jsx React.DOM */

var divStyle = {height: 10}; // rendered as "height:10px"
React.renderComponent(<div style={divStyle}>Hello World!</div>, mountNode);

See Inline Styles for more info.

Sometimes you do want to keep the CSS properties unitless. Here's a list of properties that won't get the automatic "px" suffix:

• fillOpacity
• fontWeight
• lineHeight
• opacity
• orphans
• zIndex
• zoom