obj-str

A tiny (96B) library for serializing Object values to Strings.

This module's intended use is for converting an Object with CSS class names (as keys) to a space-delimited className string. Other modules have similar goals (like classnames), but obj-str only does one thing. This is why it's only 100 bytes gzipped!

PS: I made this because Preact 8.0 removed this built-in behavior and I wanted a quick, drop-in replacement.

Install

$ npm install --save obj-str

Usage

import objstr from 'obj-str';

objstr({ foo:true, bar:false, baz:isTrue() });
//=> 'foo baz'

React

With React (or any of the React-like libraries!), you can take advantage of any props or state values in order to express conditional classes as an object.

import React from 'react';
import objstr from 'obj-str';

const TodoItem = ({ text, isDone, disabled }) => (
  <li className={ objstr({ item:true, completed:isDone, disabled }) }>
    <input type="checkbox" disabled={ disabled } checked={ isDone } />
    <label>{ text }</label>
  </li>
);

Preact

For simple use, the React example will work for Preact too. However, you may also define a custom vNode "polyfill" to automatically handle Objects when used inside className.

Note: For users of Preact 7.1 and below, you do not need this module! Your version includes this behavior out of the box!

import objstr from 'obj-str';
import { options } from 'preact';

const old = options.vnode;

options.vnode = vnode => {
  const props = vnode.attributes;
  if (props != null) {
    const k = 'class' in props ? 'class' : 'className';
    if (props[k] && typeof props[k]=='object') {
      props[k] = objstr(props[k]);
    }
  }
  old && old(vnode);
}

API

objstr(input)

input

Type: Object

A hashmap of keys & their truthy/falsey values. Booleans are preferred when speed is critically important.

babel-plugin-optimize-obj-str - Babel plugin to transform obj-str calls into optimized expressions.
clsx - Drop-in replacement for obj-str and classnames – handles all (and multiple) input types.

lukeed / obj-str

readme