What do the values ​​1, 2, and 3 in nodetype mean?

Question:

There is such a sentence in the source code of the viewer.js plugin (as abovepicture), what does it mean?

if (!element || element.nodeType !== 1) {throw new Error('The first argument is required and must be an element.');}

Parse:

All node types in JavaScript inherit from the Node type, so all node types share the same basic properties and methods.Each node has a nodeType property that indicates the type of node.

The

nodeType property returns the node type of the selected node, which allows us to know and distinguish each node in the document.

Syntax:

elementNode.nodeType

Return value: String value, representing the node type of the node.

The nodeType attribute has a total of 12 values ​​(1~12), corresponding to different nodes.The node type is represented by the following 12 constants defined in the Node type, any node type must be one of them:

Example:

alert(Node.DOCUMENT_NODE); //9alert(document.nodeType == Node.DOCUMENT_NODE)span>; //true, not valid in IEalert(document.nodeType == 9); //true for all browsing