insertBefore

The following code inserts an Element into a Text Block.

 
<!DOCTYPE HTML> 
<html> 
    <head> 
        <title>Example</title>  
    </head> 
    <body> 
        <p id="textblock">
            This is a test. 
        </p> 
        <p> 
            <button id="insert">Insert Element</button> 
        </p> 
        <script> 
            document.getElementById("insert").onclick = function() { 
                var textBlock = document.getElementById("textblock"); 
                textBlock.firstChild.splitText(10); 
                var newText = textBlock.childNodes[1].splitText(4).previousSibling; 
                textBlock.insertBefore(document.createElement("b"), newText).appendChild(newText); 
            } 
        </script> 
    </body> 
</html>

Click to view the demo