slate-reset-on-backspace.js

import { createMatcher } from '../slate-plugin-utils'

/**
 * A Slate plugin to reset empty blocks to a default type when the user presses
 * backspace at the start of a block.
 *
 * @param {Object} opts
 *   @property {String} defaultType
 *   @property {Function || Array || String} ignoreIn
 *   @property {Function || Array || String} onlyIn
 * @return {Function}
 */

function ResetOnBackspace(opts) {
  if (!opts.defaultType) throw new Error('You must provide a `defaultType` string.')

  const ignoreIn = createMatcher(opts.ignoreIn)
  const onlyIn = createMatcher(opts.onlyIn)

  /**
   * On key down.
   *
   * @param {Event} e
   * @param {Object} data
   * @param {State} state
   * @return {State}
   */

  function onKeyDown(e, data, state) {
    if (data.key != 'backspace') return
    if (state.isExpanded) return
    if (state.startOffset != 0) return
    if (ignoreIn && ignoreIn(state.startBlock)) return
    if (onlyIn && !onlyIn(state.startBlock)) return

    return state
      .transform()
      .setBlock(opts.defaultType)
      .apply()
  }

  /**
   * Return the plugin.
   */

  return {
    onKeyDown
  }
}

/**
 * Export.
 */

export default ResetOnBackspace