e commerce - Google Tag Manager and dataLayer interraction -

i use googletagmanager script , datalayer object. read in documentation datalayer object has filled above gtm script. need add product detail when user chooses product , happens after gtm script loaded. if use datalayer.push(chosenobject) action call google tag manager script? work?

yes, can push variables datalayer @ time, "trick" in how access data datalayer in tags (plus if declare datalayer above gtm code not call "push" - declare variable can push later).

it's necessary declare data in datalayer if want use page loads - standard pageview trigger run gtm code has loaded (i.e. before page has finished loading), gtm can access data preceeded in code.

triggering tags in gtm takes event (do not confuse google analytics events or javascript events, event in gtm reserved variable name).

a few events produced gtm implicitly - pageload-event, dom ready, click , submit events.

if @ later point want trigger element respond value pushed datalayer need custom event:

datalayer.push({ 'event':'i_pushed_a_value',  'payload' : 'this data' }) 

(please not data comes in key->value pairs).

now can have trigger fires on event i_pushed_a_value, , can use custom variable of type datalayer (enter key, in case payload, key in variable configuration) holds data.