node_modules/unist-util-is/index.js

'use strict'

var convert = require('./convert')

module.exports = is

is.convert = convert

// Assert if `test` passes for `node`.
// When a `parent` node is known the `index` of node should also be given.
// eslint-disable-next-line max-params
function is(node, test, index, parent, context) {
  var hasParent = parent !== null && parent !== undefined
  var hasIndex = index !== null && index !== undefined
  var check = convert(test)

  if (
    hasIndex &&
    (typeof index !== 'number' || index < 0 || index === Infinity)
  ) {
    throw new Error('Expected positive finite index or child node')
  }

  if (hasParent && (!is(parent) || !parent.children)) {
    throw new Error('Expected parent node')
  }

  if (!node || !node.type || typeof node.type !== 'string') {
    return false
  }

  if (hasParent !== hasIndex) {
    throw new Error('Expected both parent and index')
  }

  return Boolean(check.call(context, node, index, parent))
}