This is a script that grabs all your DIM items across all characters and puts them into a single array. From there you can examine, filter, etc.

DIM Getting Started

// MAIN CODE
var stuff = angular.element(document.body).injector().get('dimStoreService').getStores();
var guardian1_Items = (stuff.length >= 2) ? stuff[0].items : [];
var guardian2_Items = (stuff.length >= 3) ? stuff[1].items : [];
var guardian3_Items = (stuff.length >= 4) ? stuff[2].items : [];
var vaultItems = stuff[stuff.length - 1].items;
var allItems = guardian1_Items.concat(guardian2_Items, guardian3_Items, vaultItems);