Function extend

Creates a deep copy of the language with the given id and appends the given tokens.

If a token in reDef also appears in the copied language, then the existing token in the copied language will be overwritten at its original position.

Best practices

Since the position of overwriting tokens (token in reDef that overwrite tokens in the copied language) doesn't matter, they can technically be in any order. However, this can be confusing to others that trying to understand the language definition because, normally, the order of tokens matters in Prism grammars.

Therefore, it is encouraged to order overwriting tokens according to the positions of the overwritten tokens. Furthermore, all non-overwriting tokens should be placed after the overwriting ones.

Example

languages['css-with-colors'] = extend('css', {
  // languages.css already has a 'comment' token, so this token will overwrite CSS' 'comment' token
  // at its original position
  'comment': { ... },
  // CSS doesn't have a 'color' token, so this token will be appended
  'color': /\b(?:red|green|blue)\b/
});
Copy