list.update(newItems)

If newItems is list like the values in newItems will replace all values in list. For example:

import {DefineList} from "can";

const list = new DefineList(["A","B"]);

list.update( ["a"] );
console.log( list.serialize() ); //-> ["a"]

If newItems is an object, newItem's properties and values will be used to overwrite list's properties and values. Any enumerable properties on list that are not in newItems will be removed.

import {DefineList} from "can";

const list = new DefineList(["A","B"]);

list.update( {count: 1000, skip: 2} );

list.update( {count: 99} )
console.log( list.skip ); //-> undefined

NOTE: Use .assign() to only add properties from newItems and not delete missing items.