ui/node_modules/stylis/src/Serializer.js

import {IMPORT, LAYER, COMMENT, RULESET, DECLARATION, KEYFRAMES} from './Enum.js'
import {strlen} from './Utility.js'

/**
 * @param {object[]} children
 * @param {function} callback
 * @return {string}
 */
export function serialize (children, callback) {
	var output = ''

	for (var i = 0; i < children.length; i++)
		output += callback(children[i], i, children, callback) || ''

	return output
}

/**
 * @param {object} element
 * @param {number} index
 * @param {object[]} children
 * @param {function} callback
 * @return {string}
 */
export function stringify (element, index, children, callback) {
	switch (element.type) {
		case LAYER: if (element.children.length) break
		case IMPORT: case DECLARATION: return element.return = element.return || element.value
		case COMMENT: return ''
		case KEYFRAMES: return element.return = element.value + '{' + serialize(element.children, callback) + '}'
		case RULESET: if (!strlen(element.value = element.props.join(','))) return ''
	}

	return strlen(children = serialize(element.children, callback)) ? element.return = element.value + '{' + children + '}' : ''
}