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Runtime CSS manager, Turn CSS into dynamic JS module, Stylesheet CRUD (Create, Read, Update, Delete) in CSSOM, Solve common problems of CSS-in-JS, name space (local) class names


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CSSOBJ Join the chat at https://gitter.im/css-in-js/cssobj

Runtime CSS manager, Turn CSS into dynamic JS module, Stylesheet CRUD (Create, Read, Update, Delete) in CSSOM, Solve common problems of CSS-in-JS.

Usage - Wiki - API - Demo - React - Babel

Build Status npm Coverage Status dependencies Status Standard - JavaScript Style Guide



npm install cssobj # the lib # When use Babel npm install babel-plugin-transform-cssobj # When **NOT** use Babel, install the converter npm install -g cssobj-converter


<script src="https://unpkg.com/cssobj"></script>


First see this SIMPLE DEMO

In the example, cssobj will create <style> tag in HEAD, render CSS rules inside

import cssobj from 'cssobj' const obj = { div: { backgroundColor: 'yellow', color: 'red', // simulate 50vh in CSS3 height: () => window.innerHeight/2 + 'px' } } const result = cssobj(obj) // dynamic update height when resize window.onresize = () => result.update()

The rendered CSS (height is dynamically set to 50% of window height)

div { background-color: yellow; color: red; height: 600px; }

If you read the code, you've learned the API already:

Only One top level method: cssobj( obj, [config] ), all other things using result.someMethods, that's all, really.

Stylesheet CRUD

The power of cssobj is CSS CRUD (Create, Read, Update, Delete), dynamically change above CSS, see below:

1. Update property values

You want to change color to 'blue'

// using static value: obj.div.color = 'blue' result.update() // color is now 'blue' // using function as value: obj.div.color = function(v){ return randomColor() } result.update() // color is now random

2. Delete/Remove properties

You want to remove backgroundColor

It's just work as you expected:

delete obj.div.backgroundColor result.update()

3. Create/Add new properties

You want to add 'float' and 'clear'

It's just work as you expected:

obj.div.float = 'left' obj.div.clear = 'both' result.update()

4. Create/Add new rules

You want to add ':after' rule, and div span rule

obj.div['&:after'] = { fontSize:'10px', content:'"---"' } obj.div.span = { fontSize: '18px' } result.update()

5. Update/Replace rules

You want to replace the whole rule

obj.div.span = { color: 'green', fontSize: '20px' } result.update()

All the above can use function instead

obj.div.span = function() { return { color: randomColor(), fontSize: currentSize + 'px' } } result.update()

6. Delete/Remove rules

You want to remove div span rule

delete obj.div.span result.update()

7. Read a rule

Although cssobj can manage everything, you read the rule in stylesheet manually

const rule = result.root.children.div.omRule[0] // => CSSStyleRule rule.color = 'red'

8. Delete/Destroy cssobj

Currently, cssobj don't provide result.destroy() or similar method, you should manually destroy things:

// remove <style> tag result.cssdom.parentNode.removeChild(el) // GC result result = null

Think of this: one cssobj instance === A <style> tag with rules + A manager from JS


All @-rules work as expected, and @media can be nested at any level:

cssobj({ '.nav':{ width: '1024px', '@media print': { display: 'none' } } })

Above will hide .nav when print.

You can emit any @media rule by cssom.media option:

const result = cssobj({ '.nav':{ width: '1024px', '@media print': { color: 'red' } } }, { cssom: { media:'' } }) result.config.cssom.media = 'print' result.update()

Above will switch to print view, with below CSS:

nav {width: 1024px;} nav {color: red;}

Then switch back:

result.config.cssom.media = '' result.update() cssobj({ '@keyframes changeColor': { '0%': { backgroundColor: 'green' }, '100%': { backgroundColor: 'yellow' } }, '.nav': { backgroundColor: 'red', animation: '5s infinite changeColor' } })

Notice above @keyframes, it have to be in top level of your source object, aka cannot be nested into .nav, that is different from @media rule, which allow nested at any level, or nested into another @media:

cssobj({ h3:{ color: 'blue', '@media (min-width: 400px)': { color: 'red', '@media (max-width: 500px)': { color: 'green' } }, '@media (min-width: 500px)': { color: 'purple' } } })

Above, what's the color will be? You can take a try and see what's the final CSS will be.

There's a hidden JS Bin...

Localize class names

Passing local: true as option, cssobj will add a random name space into all class names, this is called localize:

const result = cssobj( { '.nav': {color: 'red'} }, { local: true } )

Rendered CSS:

.nav_1lwyllh4_ {color: red;}

You can get this name space using result.space, or using below methods:

// As HTML class attribute result.mapClass('nav active') // [string] 'nav_1lwyllh4_ active_1lwyllh4_' // As CSS selector result.mapSel('.nav li.item') // [string] '.nav_1lwyllh4_ li.item_1lwyllh4_'


You can use react-cssobj with React

Work Flow with Babel, See also Without Babel Version

If use Babel, recommended the babel-plugin-transform-cssobj

// create <style> in <head>, insert CSS rules, random namespace: _1jkhrb92_ // The babel-plugin only transform: CSSOBJ `text` const result = CSSOBJ ` --- # cssobj config local: true plugins: - default-unit: px --- // SCSS style (nested) .nav { color: blue; height: 100; // font-size is a function .item { color: red; font-size: ${v => v.raw ? v.raw + 1 : 12} } // nested @media @media (max-width: 800px) { color: #333; // & = parent selector = .nav &:active { color: #666; } } } ` const html = result.mapClass(<ul class='nav'><li class='item active'>ITEM</li></ul>) // <ul class="nav_1jkhrb92_"><li class="item_1jkhrb92_ active_1jkhrb92_"></li></ul>

Rendered result as below:

import cssobj from "cssobj"; import cssobj_plugin_default_unit from "cssobj-plugin-default-unit"; const result = cssobj({ '.nav': { color: 'blue', height: 100, '.item': { color: 'red', fontSize: v => v.raw ? v.raw + 1 : 12 }, '@media (max-width: 800px)': { color: '#333', '&:active': { color: '#666' } } } }, { local: true, plugins: [cssobj_plugin_default_unit('px')] }); const html = <ul class={result.mapClass('nav')}><li class={result.mapClass('item active')}></li></ul>

For this first time render, all class names add a random suffix _1jkhrb92_, the font-size is 12px, the <style> tag which cssobj created now contains:

.nav_1jkhrb92_ { color: blue; height: 100px; } .nav_1jkhrb92_ .item_1jkhrb92_ { color: red; font-size: 12px; } @media (max-width: 800px) { .nav_1jkhrb92_ { color: rgb(51, 51, 51); } .nav_1jkhrb92_:active { color: rgb(102, 102, 102); } }

Update CSS Value

Since we already have a function as the value:

fontSize: v => v.raw ? v.raw + 1 : 12

  • the value (===v.raw) initialised with 12 (default-unit plugin will add px when rendering, that is v.cooked === 12px)

  • each call of the function will increase font-size by 1

So, just need call result.update, the function invoked, stylesheet updated, automatically:

result.update() // font-size -> 13px result.update() // font-size -> 14px

Above, only font-size changed, all other things keep untouched

CRUD (Create, Read, Update, Delete) stylesheet from JS

When the source JS Object (first arg of cssobj()) have no changes, result.update only invoke the value function (here, the above font-size function),

Otherwise, it will look into the source JS Object, find which part have been changed (diff), and update stylesheet accordingly. See below:

// result.obj === reference of the source js object // change a css property result.obj['.nav'].color = 'orange' // remove a css property delete result.obj['.nav'].height // add a new css property result.obj['.nav'].width = 200 // add a new rule result.obj['.nav'].a = { color: 'blue', '&:hover': {textDecoration: 'none'} } // delete a rule delete result.obj['.nav']['.item'] result.update() // color -> 'orange' (PROP CHANGED) // height -> (PROP REMOVED) // width -> 200px (PROP ADDED) // a, a:hover -> (RULE ADDED) // .item -> (RULE REMOVED)

Above, only diffed part updated, other rules and props will keep untouched

Now, the stylesheet becomes:

.nav_1jkhrb92_ { color: orange; width: 200px; } @media (max-width: 800px) { .nav_1jkhrb92_ { color: #333; } .nav_1jkhrb92_:active { color: #666; } } .nav_1jkhrb92_ a { color: blue; } .nav_1jkhrb92_ a:hover { text-decoration: none; }

Diff with NEW JS Object

const newObj = { '.nav': { width: 100, a: { color: 'blue' } } } result.update(newObj) // cssobj will DIFF with old obj, keep same part, change diffed part in stylesheet! // .nav, .nav a rules keeped // width -> 100px, drop all other rules/props

Now, the stylesheet becomes:

/* below 2 rules keeped */ .nav_1jkhrb92_ { width: 100px; } .nav_1jkhrb92_ a { color: blue; } /* other rules gone */

That's it, see more Usage & Example

Work Flow (Without Babel)

First install cssobj-converter

npm install -g cssobj-converter
  • Step 1

Write your CSS as normal (e.g. index.css)

// file: index.css .nav { color: blue; font-size: 12px; }
  • Step 2

Turn it into JS module, from cssobj-converter CLI

# in command line, run cssobj-converter cssobj index.css -o index.css.js

The result

// file: index.css.js module.exports = { '.nav': { color: 'blue', fontSize: '12px' } }
  • Step 3

Let's rock:

// import your css module const obj = require('./index.css') // create <style> tag in <head>, with rules in obj. // `local: true` will put class names into local space const result = cssobj(obj, {local: true}) result.mapClass(<JSX>) // with Babel result.mapClass('classA') // without Babel // update some rule obj['.nav'].color = 'red' obj['.nav'].fontSize = v => parseInt(v.cooked) + 1 // increase font-size by 1 result.update()

Documented API

More to read:

How it worked?

  1. cssobj first parse js object into Virtual CSSOM middle format.

  2. The internal cssom plugin will create stylesheet dom, and apply rules from middle format.

  3. When the js object changed, cssobj will diff CSSOM rules (add/delete/change) accordingly. (see demo)


Convert existing style sheet into cssobj:

  • CLI Converter Recommended CLI tools to convert CSS. Run npm -g cssobj-converter

  • Online Converter It's free node server, slow, and unstalbe, not recommended



About writing a plugin, See: plugin-guide




Using phantom 2.0 to test with CSSOM. Please see test/ folder.


cssobj is wrapper for cssobj-core, plugin-localize and plugin-cssom.






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