encodeBlock.js

import updateMutation from './util/updateMutation'
import rangeSort from './util/rangeSort'

const ENTITY_MAP = {
  '&': '&',
  '<': '&lt;',
  '>': '&gt;',
  '"': '&quot;',
  "'": '&#x27;',
  '`': '&#x60;',
  '\n': '<br/>',
}

export default (block) => {
  const blockText = [...block.text]

  let entities = block.entityRanges.sort(rangeSort)
  let styles = block.inlineStyleRanges.sort(rangeSort)
  let resultText = ''

  for (let index = 0; index < blockText.length; index += 1) {
    const char = blockText[index]

    if (ENTITY_MAP[char] !== undefined) {
      const encoded = ENTITY_MAP[char]
      const resultIndex = [...resultText].length
      resultText += encoded

      const updateForChar = (mutation) =>
        updateMutation(mutation, resultIndex, char.length, encoded.length, 0, 0)

      entities = entities.map(updateForChar)
      styles = styles.map(updateForChar)
    } else {
      resultText += char
    }
  }

  return {
    ...block,
    text: resultText,
    inlineStyleRanges: styles,
    entityRanges: entities,
  }
}