In Adobe Target you don’t fetch a library offer arbitrarily from the browser. Offers are returned only through a decision (activity + location/mbox) using at.js (client-side) or the Delivery API (typically server-side). The browser asks Target for content for a location (mbox); Target decides which offer to return and you apply it.
Instead of calling the offer id directly you can instead get a similar result through an Activity in Adobe Target. Here are the steps, this approach uses One mbox, multiple experiences, it's cleaner and Switchs variants via params.
1) Create an XT (Experience Targeting) activity.
2) Tie each variant (experience) to an HTML offer (that you want to call directly on page).
3) Define unique mbox parameters that supposed to delivery the Variant tied to the desired HTML offer.
4) Create seperate audiences in that match the mbox parameter you’ll pass from the client.
5) Call Target with that mbox + parameter and Target's delivery engine will fetch the desired variant/HTML offer
Alternatively you can also setup Multiple mboxes, one offer each Experience Activity in Target and call the right mbox at runtime.
It always a best practice to set a default experience to avoid rendering issues if your activity rules doesn't match.
