Create and build a function

Create a function in Studio, write its handler, save a draft, and compile it to a running WebAssembly version.

4 min read

At the end, the function is Ready but not yet triggered by anything. You wire it up on the page for its kind: platform event or hook.

Before you begin

  • Your user role must be Admin. Contributors cannot see the Functions surface.
  • You must be working in the Global organisation. The Functions tab only appears there.
  • Decide the function's kind first. It is permanent.
  • If your handler will call an external API, have the hostnames ready. You will need to allow-list them before any outbound call works.

Open the Functions tab

  1. In the organisation switcher at the top of the sidebar, choose Global.

    Organisation switcher open, with Global highlighted

  2. In the sidebar, select General Settings.

    Studio menu on Global, with General Settings highlighted

    The Enterprise Settings page opens.

  3. Select the Functions tab.

    Enterprise Settings with the Functions tab highlighted

Create the function

On the Functions tab:

  1. Select New function.

    Functions tab with the New function button highlighted

  2. Enter the Display name, such as Loyalty award processor. The identifier is generated for you.

    Create function window with the Display name Loyalty award processor, highlighted

  3. Under Kind, choose Platform event or Hook. This choice is permanent.

    Create function window with the Platform event kind selected, highlighted

  4. (Hook only) Under Hook point, choose the hook point, here contact.verify — Contact verification.

    Create function window with Hook chosen and the Hook point contact.verify, highlighted

    Hook point starts on contact.create.pre — Contact create (pre), and it's permanent too: the function can only ever bind there.

  5. Select Create.

    Create function window with the Create button highlighted

Each kind or hook point you choose drops a working starter handler into Source (TypeScript), until you edit the code yourself. OmniLab type-checks the source and saves the function as Draft.

Write your handler and save the draft

  1. On the function's row, select Edit.

    Functions tab with Edit on the Touchpoint completion logger row highlighted

  2. On the Source tab, write your handler.

    Source tab with the handler in the editor, highlighted

  3. Select Save source.

    Source tab with the Save source button highlighted

Your file must export the name that matches your kind, or saving fails with a type error. The starter handler already exports the right name and compiles as-is, so you can build it unchanged to check the setup.

The contact.verify starter reads the secret brevo.api_key, in lowercase. Secret keys are case-sensitive, so change it to match the key you create in your bundle, such as brevo.API_KEY.

Working examples for each kind, from a hello world up, are on Platform event functions and Hook functions.

  • The editor shows a live size counter against the 1 MB source ceiling. The entry point is user.ts.
  • Save source stays greyed out until you change something.
  • Saving stores and type-checks your code. It doesn't deploy anything: a live function keeps serving its current version until you build.
  • If the type check fails, a Lint failed panel lists each problem with its file, line and column. Select a row to jump to it. Nothing is saved while the check fails.

Build it

In the function's editor:

  1. Select the Build tab.

    Function editor with the Build tab highlighted

  2. Select Build.

    Build tab with the Build button highlighted, and the current build Ready

The status changes to Building, then Ready, usually within a minute: the version number goes up, and WASM sha and WASM size fill in. If the build fails, the tab shows the error and a truncated build log. Rebuilding unchanged source returns almost at once.

Confirm it runs

Before you wire it up, run a test invocation from the function's Test tab.

If something's blocked

  • The Functions tab is not there: you are either not an Admin, or not in the Global organisation. Switch organisation with the picker at the top of the sidebar.
  • Saving reports a type error you don't recognise: the most common cause is the export name. A hook function for contact.create.pre must export exactly onContactCreatePre; a platform event function must export onPlatformEvent. The name is derived from the kind and hook point, and a mismatch is reported as a missing or wrongly shaped export. A handler that doesn't match its declared type fails the same way: a wrong parameter, a wrong return value, or the wrong handler type imported for the kind. Compare your handler against the example on your kind's page.
  • The build has been Building for a long time: a build that stalls is released after about fifteen minutes, and you can then start another. If it happens repeatedly, contact support with the build id from the Build tab.
  • Your handler cannot reach an external API: a function with no allowed hosts is refused every outbound request. See Configure runtime and secrets.
  • The function is Ready but nothing happens: a built function is not triggered by anything until you add a subscription or a hook binding.

Next steps

On this page

Before you beginOpen the Functions tabCreate the functionWrite your handler and save the draftBuild itConfirm it runsIf something's blockedNext steps