function del($item) {
    console.log($item.data())
    console.log($item.data('id'))
}

Object {id: 12345"}

12345

Object
    id: 12345
    __proto__: Object
        __defineGetter__: function __defineGetter__() { [native code] }
        __defineSetter__: function __defineSetter__() { [native code] }
        __lookupGetter__: function __lookupGetter__() { [native code] }
        __lookupSetter__: function __lookupSetter__() { [native code] }
        constructor: function Object() { [native code] }
        hasOwnProperty: function hasOwnProperty() { [native code] }
        isPrototypeOf: function isPrototypeOf() { [native code] }
        propertyIsEnumerable: function propertyIsEnumerable() { [native code] }
        toLocaleString: function toLocaleString() { [native code] }
        toString: function toString() { [native code] }
        valueOf: function valueOf() { [native code] }

undefined