How to insert sibling node before the current node

You can use ChildNode.before ()

var P = document.createElement ( 'P' );
 var P1 = document.createElement ( 'P' ); 

// insert element node 
el.before (P); 

// Insert text node 
el.before ( 'the Hello' ); 

// insert element node plurality 
el.before (P, P1); 

// insert element nodes and text nodes 
el.before (p, 'Hello') ;

 

note: 

1 can be inserted into an element node, a text node may be inserted;

2. A node may be inserted, may be inserted into the plurality of nodes;

3. The current element must have a parent node;