planning

node_modules/hast-util-is-element/index.js

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+'use strict'
+
+var convert = require('./convert')
+
+module.exports = isElement
+
+isElement.convert = convert
+
+// Check if if `node` is an `element` and whether it passes the given test.
+function isElement(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 for child node')
+  }
+
+  if (hasParent && (!parent.type || !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 check.call(context, node, index, parent)
+}