readme.md

hast-util-assert

hast utility to assert trees.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • assert(tree[, parent])
  • parent(tree[, parent])
  • literal(node[, parent])
  • _void(node[, parent])
  • wrap(fn)
  • AssertionError
• Types
• Compatibility
• Security
• Related
• Contribute
• License

What is this?

This package is a tiny utility that helps you deal with nodes.

When should I use this?

This utility is typically useful when you expect certain nodes in your APIs and want to make sure they’re valid and as expected.

A different utility, unist-util-assert, does the same but for any unist node.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install hast-util-assert

In Deno with esm.sh:

import {assert} from 'https://esm.sh/hast-util-assert@4'

In browsers with esm.sh:

<script type="module">
  import {assert} from 'https://esm.sh/hast-util-assert@4?bundle'
</script>

Use

import {assert} from 'hast-util-assert'

assert({type: 'root', children: []})
assert({type: 'element', tagName: 'a', properties: {}, children: []})
// All OK.

assert({children: []})
// AssertionError: node should have a type: `{ children: [] }`

assert({type: 'element', properties: {}, children: []})
// AssertionError: `element` should have a `tagName`: `{ type: 'element', properties: {}, children: [] }`

API

This package exports the identifiers _void, assert, literal, parent, and wrap. There is no default export.

assert(tree[, parent])

Assert that tree is a valid hast Node.

If tree is a parent, all children will be asserted too.

Supports unknown hast nodes.

Parameters

• tree (unknown) — thing to assert
• parent (Parent, optional) — optional, valid parent

Returns

Nothing.

Throws

When tree (or its descendants) is not a hast node (AssertionError).

parent(tree[, parent])

Assert that tree is a valid hast Parent.

All children will be asserted too.

Supports unknown hast nodes.

Parameters

• tree (unknown) — thing to assert
• parent (Parent, optional) — optional, valid parent

Returns

Nothing.

Throws

When tree is not a parent or its descendants are not nodes (AssertionError)

literal(node[, parent])

Assert that node is a valid hast Literal.

Supports unknown hast nodes.

Parameters

• node (unknown) — thing to assert
• parent (Parent, optional) — optional, valid parent

Returns

Nothing.

Throws

When node is not a hast literal (AssertionError).

_void(node[, parent])

Re-exported from unist-util-assert.

wrap(fn)

Re-exported from unist-util-assert.

AssertionError

Re-exported from unist-util-assert.

Types

This package is fully typed with TypeScript. It exports the additional type AssertionError.

Compatibility

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, hast-util-assert@^4, compatible with Node.js 16.

Security

hast-util-assert does not change the syntax tree so there are no openings for cross-site scripting (XSS) attacks.

Related

• unist-util-assert — check unist nodes
• mdast-util-assert — check mdast nodes
• nlcst-test — check nlcst nodes

Contribute

See contributing.md in syntax-tree/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

License

MIT © Titus Wormer