React util function to find and replace string with links in a label

flattenArray.js

const flattenArray = (arr) => arr.reduce((result, value) => result.concat(value), [])

getLabelWithLinks.js

// const termsLabel = "By checking this box you agree to our terms"
//
// const links = [
//   { href: "https://something.com", title: "By checking" },
//   { href: "https://somewhere.com", title: "this box" },
// ]
//
// const { label, unmatched } = getLabelWithLinks(termsLabel, links)
//
// `label` will be something like:
//   `<span>["", <a href="https://something.com">By checking</a>, " ", <a href="https://somewhere.com">this box</a>, " you agree to our terms", ""]</span>`

const getLabelWithLinks = (label, links) => {
  const [matched, unmatched] = links.reduce((result, link) => {
    result[label.indexOf(link.title) !== -1) ? 0 : 1].push(link)
    return result
  }, [[], []])

  if (!matched.length) {
    return { label, unmatched }
  }

  let labelResult = matched.reduce((result, link) => {
    result = result.map(part => {
      // if it's not a string OR it is but doesn't contain the link title
      if (typeof part !== "string" || part.indexOf(link.title) === -1) {
        return part
      }

      // split on the title (return an array of [beforeTitle, afterTitle]), and then insert the link in the middle
      part = part.split(link.title)
      return [part[0], <Link key={`${link.title}-${link.href}`} link={link}>{link.title}</Link>, part[1]]
    })

    return flattenArray(result)
  }, [label])

  labelResult = <span>{labelResult}</span>

  return { label: labelResult, unmatched }
}