defaultLowlight

  import {createLowlight} from 'lowlight'
  import xml from 'highlight.js/lib/languages/xml'

  const lowlight = createLowlight()

  lowlight.register({xml})

  // Note: `html` is an alias for `xml`.
  console.log(lowlight.highlight('html', '<em>Emphasis</em>'))

{type: 'root', children: [Array], data: {language: 'html', relevance: 2}}

  import {createLowlight} from 'lowlight'
  import xml from 'highlight.js/lib/languages/xml'

  const lowlight = createLowlight()

  lowlight.register({xml})

  // Note: `html` is an alias for `xml`.
  console.log(lowlight.highlight('html', '<em>Emphasis</em>'))

{type: 'root', children: [Array], data: {language: 'html', relevance: 2}}

  import {createLowlight} from 'lowlight'
  import markdown from 'highlight.js/lib/languages/markdown'

  const lowlight = createLowlight()

  lowlight.register({markdown})

  // lowlight.highlight('mdown', '<em>Emphasis</em>')
  // ^ would throw: Error: Unknown language: `mdown` is not registered

  lowlight.registerAlias({markdown: ['mdown', 'mkdn', 'mdwn', 'ron']})
  lowlight.highlight('mdown', '<em>Emphasis</em>')
  // ^ Works!

  import {createLowlight} from 'lowlight'
  import markdown from 'highlight.js/lib/languages/markdown'

  const lowlight = createLowlight()

  lowlight.register({markdown})

  // lowlight.highlight('mdown', '<em>Emphasis</em>')
  // ^ would throw: Error: Unknown language: `mdown` is not registered

  lowlight.registerAlias({markdown: ['mdown', 'mkdn', 'mdwn', 'ron']})
  lowlight.highlight('mdown', '<em>Emphasis</em>')
  // ^ Works!