Transformers

Shiki uses hast, a AST format for HTML, to process the result and generate the HTML.

You can provide your own transformers to customize the generated HTML by manipulating the hast tree. You can pass custom functions to modify the tree for different types of nodes. For example:

import { codeToHtml } from 'shiki'

const code = await codeToHtml('foo\bar', {
  lang: 'js',
  theme: 'vitesse-light',
  transformers: [
    {
      code(node) {
        this.addClassToHast(node, 'language-js')
      },
      line(node, line) {
        node.properties['data-line'] = line
        if ([1, 3, 4].includes(line))
          this.addClassToHast(node, 'highlight')
      },
      span(node, line, col) {
        node.properties['data-token'] = `token:${line}:${col}`
      },
    },
  ]
})

We also provide some common transformers for you to use, see @shikijs/transforms and `@shikijs/colorized-brackets for more details.

Transformer Hooks

• preprocess - Called before the code is tokenized. You can use this to modify the code before it is tokenized.
• tokens - Called after the code is tokenized. You can use this to modify the tokens.
• span - Called for each <span> tag, for each token.
• line - Called for each line <span> tag.
• code - Called for each <code> tag, wraps all the lines.
• pre - Called for each <pre> tag, wraps the <code> tag.
• root - The root of HAST tree. Usually with only one child <pre> tag.
• postprocess - Called after the HTML is generated, get a chance to modify the final output. Will not be called in codeToHast.

Meta

Transformers can also access markdown 'meta' strings in supported integrations.

```html foo=bar baz-qux="qu ux"

You can access the raw meta using:

options.meta
// => { __raw: 'foo=bar baz-qux="qu ux"' }