how to select previous node indesign javascript

you  can access previous siblings or child by using

var myDoc = app.documents[0];

var xPath = "//kwd-group"
var root = myDoc.xmlElements[0];
var node = null;
var proc = app.xmlRuleProcessors.add([xPath]);
var match = proc.startProcessingRuleSet(root);
while (match != undefined) {
node = match.element;
match = proc.findNextMatch();
if (node != null && node != undefined) {

node.parent.xmlElements[node.index-1]/////////////this will give previous Node

}

}

Can you add more details as to what is the node that you are reffering to. Add in some code snippet that you have written and is not working as expected, or give some screenshots of the document if you don't even know where to start with your code. Just a terse statement is not going to help us in helping you

-Manan