Native js implementation adds content to the specified element after it

var header1 = ("header");
var p = ("p"); // Create an element node
insertAfter(p,header1); // Because js does not directly append the method behind the specified element, you need to create a method yourself
function insertAfter( newElement, targetElement ){ // newElement is the element to be appended targetElement is the location of the specified element
var parent = ; // Find the parent node of the specified element
if( == targetElement ){ // Determine whether the specified element is the last position in the node. If so, use the appendChild method directly
( newElement, targetElement );
}else{
( newElement, );
};
};