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unist utility to assert trees.

• 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
• Extensions
• Types
• Compatibility
• Related
• Contribute
• License

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

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

Different utilities,mdast-util-assert,hast-util-assert, andnlcst-test,do the same but for mdast, hast, and nlcst nodes, respectively.

This package isESM only.In Node.js (version 16+), install withnpm:

npm install unist-util-assert

In Deno withesm.sh:

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

In browsers withesm.sh:

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

import{_void,assert,parent}from'unist-util-assert'assert({type:'root',children:[]})assert({type:'break'})assert({type:'element',properties:{},children:[]})// All OK.assert({children:[]})// AssertionError: node should have a type: `{ children: [] }`parent({type:'break'})// AssertionError: parent should have `children`: `{ type: 'break' }`assert({type:'element',properties:function(){}})// AssertionError: non-specced property `properties` should be JSON: `{ type: 'element', properties: [Function] }`_void({type:'text',value:'Alpha'})// AssertionError: void should not have `value`: `{ type: 'text', value: 'Alpha' }`assert({type:'paragraph',children:['foo']})// AssertionError: node should be an object: `'foo'` in `{ type: 'paragraph', children: [ 'foo' ] }`

This package exports the identifiers_void,assert,literal,parent, andwrap.There is no default export.

Assert thattree is a valid unistNode.

Iftree is a parent, all children will be asserted too.

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

Nothing.

Whentree (or its descendants) is not a node.

Assert thattree is a valid unistParent.

All children will be asserted too.

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

Nothing.

Whentree is not a parent or its descendants are not nodes.

Assert thatnode is a valid unistLiteral.

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

Nothing.

Whennode is not a literal.

Assert thatnode is a valid void node.

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

Nothing.

Whennode is not a node, a parent, or a literal.

Wrapper that adds the current node (and parent, if available) to errormessages.

• fn ((node?: any, parent?: Parent | null | undefined) => asserts node is Node))— custom assertion

Wrappedfn.

Assertion error fromnode:assert (TypeScript type).

typeAssertionError=import('node:assert').AssertionError

This module can be used as a base to test subsets of unist (for an example, seemdast-util-assert).All functions that are exposed from such a module, and functions used internallyto test children, should be wrapped inwrap, which adds an inspectable stringof the respective node, and its parent when available, to the exposed errormessage.

This package is fully typed withTypeScript.It exports the additional typeAssertionError.

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

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

• mdast-util-assert— assert mdast nodes
• hast-util-assert— assert hast nodes
• nlcst-test— assert nlcst nodes

Seecontributing.md insyntax-tree/.github forways to get started.Seesupport.md for ways to get help.

This project has acode of conduct.By interacting with this repository, organization, or community you agree toabide by its terms.

MIT ©Titus Wormer