CODE EXAMPLE FOR JAVASCRIPT

javascript range setstart

var range = document.createRange();
var root_node = document.getElementById("test");

// Start at the `<p>` element.
range.setStart(root_node, 1); 

// End in the `ello` text node, between the two `l`s.
range.setEnd(root_node.childNodes[2], 2); 

var newNode = document.createElement("b");

range.surroundContents(newNode);