Replace special chars in javascript

Hi all.

I'm using this Javascript to autopopulate ctrlField4 with info from field 1 and 2 in function OnPageLoad. What i need is a way to replace special chars at the same time.
Anyone have any idea to acomplish this?

var ctrlField1 = Runner.getControl(pageid, 'givenName');
var ctrlField2 = Runner.getControl(pageid, 'sn');
var ctrlField3 = Runner.getControl(pageid, 'cn');
var ctrlField4 = Runner.getControl(pageid, 'userPricipalName');

function func() {
ctrlField3.setValue(ctrlField1.getValue() + " " + ctrlField2.getValue());
ctrlField4.setValue(ctrlField1.getValue() + "." + ctrlField2.getValue());
};
ctrlField2.on('keyup', func);
ctrlField3.on('keyup', func);