You can use the rpc method in JavaScript to call the search method on the ir.actions.act_window model to get the action ID using the external ID. Here is an example code snippet that you can use:

javascript

var external_id = 'model.action_id';
var model = 'ir.actions.act_window';
rpc.query({
model: model,
method: 'search',
args: [['xml_id', '=', external_id]],
context: session.user_context,
}).then(function(ids) {
if (ids.length > 0) {
var action_id = ids[0];
console.log('Action ID: ' + action_id);
}
});

This code will search for the ir.actions.act_window record with the specified xml_id (which is the external ID) and return the ID of the first record found. You can then use the action_id variable to perform other operations with the action, such as opening it.