styles-merge/index.js

A JavaScript utility for merging style objects together

'use strict'

/**
 * A simple utility to conditionally evaluate style properties
 * and merge them into a single one.
 *
 * @returns {Object}
 */
function StylesMerge () {
  const self = this

  return function (...stylePredicatePairs) {
    let mergedStyles = stylePredicatePairs.reduce((o, pair) => ({ ...o, ...pair }), {})

    /**
     * Prototype method for an 'if-then' semantic.
     *
     * @param {Boolean} argIf
     * @param {Object} argThen
     * @returns {Object}
     */
    self.ifThen = (argIf, argThen) => {
      if (argIf === true) {
        mergedStyles = { ...mergedStyles, ...(argThen || {}) }
      }

      return self
    }

    /**
     * Prototype method for an 'if-then-else' semantic.
     *
     * @param {Boolean} argIf
     * @param {Object} argThen
     * @param {Object} argElse
     * @returns {Object}
     */
    self.ifThenElse = (argIf, argThen, argElse) => {
      if (argIf === true) {
        mergedStyles = { ...mergedStyles, ...(argThen || {}) }
      } else {
        mergedStyles = { ...mergedStyles, ...(argElse || {}) }
      }

      return self
    }

    /**
     * Return the evaulated styles.
     *
     * @returns {Object}
     */
    self.eval = () => {
      return mergedStyles
    }

    return self
  }
}

module.exports = new StylesMerge()