js insert before first child code example

Example 1: js insertbefore

// The Node.insertBefore() method inserts a node before a
// reference node as a child of a specified parent node.
let insertedNode = parentNode.insertBefore(newNode, referenceNode)

Example 2: javascript append how first element

var eElement; // some E DOM instance
var newFirstElement; //element which should be first in E

eElement.insertBefore(newFirstElement, eElement.firstChild);