> For the complete documentation index, see [llms.txt](https://radlohead.gitbook.io/typescript-deep-dive/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://radlohead.gitbook.io/typescript-deep-dive/overview/ast/ast-trivia.md).

# Trivia

Trivia (called that because it's `trivial`) represent the parts of the source text that are largely insignificant for normal understanding of the code. For example; whitespace, comments, and even conflict markers. Trivia is *not stored* in the AST (to keep it lightweight). However, it can be fetched *on demand* using a few `ts.*` APIs.

Before we show them you need to understand the following:

## Trivia Ownership

In General:

* A token owns any trivia after it on the *same* line *upto* the next token.
* Any comment *after that line* is associated with the following token.

For leading and ending comments in a file:

* The first token in the source file gets all the initial trivia.
* The last sequence of trivia in the file is tacked onto the end-of-file token, which otherwise has zero width.

## Trivia APIs

For most basic uses, comments are the "interesting" trivia. The comments that belong to a Node can be fetched through the following functions:

| Function                      | Description                                                                                                                                                                                                        |
| ----------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `ts.getLeadingCommentRanges`  | Given the source text and position within that text, returns ranges of comments between the first line break following the given position and the token itself (probably most useful with `ts.Node.getFullStart`). |
| `ts.getTrailingCommentRanges` | Given the source text and position within that text, returns ranges of comments until the first line break following the given position (probably most useful with `ts.Node.getEnd`).                              |

As an example, imagine this portion of a source file:

```typescript
debugger;/*hello*/
    //bye
  /*hi*/    function
```

`getLeadingCommentRanges` for the `function` will only return the last 2 comments `//bye` and `/*hi*/`.

Appropriately, calling `getTrailingCommentRanges` on the end of the debugger statement will extract the `/*hello*/` comment.

## Token Start/Full Start

Nodes have what is called a "token start" and a "full start".

* Token Start: the more natural version, which is the position in file where the text of a token begins
* Full Start: the point at which the scanner began scanning since the last significant token

AST nodes have an API for `getStart` and `getFullStart`. In the following example:

```typescript
debugger;/*hello*/
    //bye
  /*hi*/    function
```

for `function` the token start is at `function` whereas *full* start is at `/*hello*/`. Note that full start even includes the trivia that would otherwise be owned by the previous node.


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