sumThe sum function returns a number that is the sum of the numeric values of each node in a given node-set.Syntaxsum(node-set) Arguments node-set The node-set to be evaluated. Each node in this node-set is evaluated as if it were passed to the number() function, and a sum of the resulting numbers is returned. ReturnsA number.NotesNone.DefinedXPath 1.0 4.3Gecko supportSupported.