Convert DraftJS ContentState to html (only plaintext and mentions)

convertDraftToHTML.js

// @flow
import { RawDraftContentState } from 'draft-js'

type Mention = {
    link: string,
    name: string,
    fullName: ?string,
    id: number,
    avatar: string
}


export const createUserLinkFromMention = (mention: Mention):string => {
    return `<a href="${mention.link}" data-userid="${mention.id}">@${mention.name}</a>`
}

export default (rawContentState: RawDraftContentState):string => {
    const { blocks, entityMap } = rawContentState
    
    return blocks.map(block => {
        const ranges = block.entityRanges.concat()
            .sort((r1, r2) => r2.offset - r1.offset)
        return ranges.reduce((string, range) => {
            const mentionLink = createUserLinkFromMention(entityMap[range.key].data.mention)
            return string.substring(0, range.offset) + mentionLink + string.substring(range.offset + range.length)
        }, block.text)
    }).join('')
}