🤔 Decider

Apply CSS to React components conditionally.

className={decide(styles, {
    header: true,
    mobile: props.isMobile,
    narrow: parseInt(props.width) < 400,
    hidden: (props.hidden !== "false" && Boolean(props.hidden)),
    fixed: parseInt(props.width) >= 400 || !props.isMobile
})}

Why?

Sometimes you need to switch class names conditionally. Here are some examples:

• You have a shopping cart which can be either cart or cart empty according to its props;
• You have a Header component. Its class name is always header, but on a mobile device, it should be also mobile. Oh, and if the width prop is less than '400px', it should also be narrow. Oh, and it should be hidden when either hidden prop is truthy but not equals to "false" string, and it should also be fixed when it is neither narrow nor mobile.

Installation

npm i --save textpain/decider

Syntax

import decide from 'decider'

decide(styles, {
  className: condition
})

The first argument is your styles imported as a CSS module. The second is decision matrix, where keys are class names, and values are conditions that will be interpreted as boolean values. If it's true, the corresponding class name will be applied.

Example

import decide from 'decider'
import styles from './header.module.css'

export default props => (
  <header className={ decide(styles, {
  
    // 'header' class name is always applied
    header: true,
    
    // 'mobile' class name will apply if 'mobile' prop is truthy, so the result would be 'header mobile'
    mobile: props.mobile,
    
    // 'fixed' would be applied either if there's an explicitly set 'fixed' prop, or if the 'mobile' prop is falsy
    fixed: props.fixed || !props.mobile,
    
    // 'narrow' class name would be applied if 'width' prop is less than 400
    narrow: props.width < 400
  })} >
    ...
  </header>
)

Differences from classnames

• decide is a pure function. It works with CSS modules without bind magic, so you can use it virtually anywhere.
• Smaller bundle size: Decider is around 176 bytes gzipped!
• Syntax was much easier for me to adopt.