Lodash isElement: How It Confirms a DOM Node

The Lodash _.isElement utility provides a reliable way to verify whether a given JavaScript value is a DOM element. This article breaks down the internal checks and exact properties Lodash inspects—specifically the nodeType property, the object-like type status, and prototype validation—to reliably distinguish real DOM elements from plain objects or other data types.

Under the hood, Lodash implements _.isElement with the following logical condition:

function isElement(value) {
  return isObjectLike(value) && value.nodeType === 1 && !isPlainObject(value);
}

To determine whether the input is a valid DOM element, Lodash inspects three primary criteria:

1. Object-Like Structure (isObjectLike)

Before checking DOM-specific attributes, Lodash verifies that the value is "object-like." This requires two conditions:

• The value must not be null.
• The typeof operator must return 'object'.

This preliminary step filters out primitives (such as strings, numbers, and booleans) as well as undefined and functions, preventing runtime errors when accessing properties in the next steps.

2. The nodeType Property

The primary property inspected is nodeType. Lodash checks that:

value.nodeType === 1

In the W3C DOM specification, every DOM node exposes a numeric nodeType property. A value of 1 corresponds to Node.ELEMENT_NODE (such as <div>, <p>, or <span>). This distinguishes element nodes from other DOM node types, such as text nodes (nodeType === 3), comment nodes (nodeType === 8), and document fragments (nodeType === 11).

3. Exclusion of Plain Objects (!isPlainObject)

To prevent false positives from mock objects or custom object literals, Lodash verifies that the value is not a plain object:

!isPlainObject(value)

A standard object literal like { nodeType: 1 } satisfies the nodeType === 1 check. By verifying that the object's prototype does not directly inherit from Object.prototype (or null), Lodash ensures that only host objects or instances derived from browser DOM classes (such as HTMLElement or Element) pass the test.