Custom code - API

Custom code in formulas and actions is almost entirely vanilla javascript. However, there is a thin API to access toddle internals that you might find useful.

Custom actions and formulas can contain any number of functions, but they must contain their entry function. The entry function is named the same as your code file. If your file is called showModal then your entry function is called:

☝️ function showModal(args, ctx) {


Formulas are functions. Given some inputs, they produce an output. This could be Add , which takes a and b and returns them added together. Almost all common functions exist as built-in formulas in toddle already. We've found that by composing the built-in formulas, you can achieve almost anything.

☝️ Formulas are synchronous, so you should not use Promises , Fetch or similar asynchronous APIs in your custom formulas. Instead, for such cases you can use an asynchronous custom action with a callback to another workflow with the value. You can then use the callback to set a variable that can be used in your formulas.


toddle expects exactly one function to have the same name as your custom action. This is the entry point. It is called with two arguments:

  • The first is an object with the arguments that the action is called by. If your action has an argument called "foo" that is called with "bar", then your arguments object will look like `{ foo: "bar" }`
  • The second argument is your current context. This context contains a function "triggerActionEvent" that is used to trigger your events.

Unlike formulas, actions do not have a return-value. Instead, actions may call other workflows with the triggerActionEvent . Events can be called asynchronously, so you could for example use a setTimeout , and then call your triggerActionEvent to call another workflow after a wait. This is exactly what the build-in sleep action does in toddle. toddle actions and formulas are built in exactly the same way as your custom code.

☝️ Warning: Formulas and actions can run any code you put into them, so be careful of malicious attempts when you paste code-snippets onto your app. Additionally, formulas should not contain side-effects, leave this to actions. If a formula is not a pure function then it might cause you some nasty bugs and reduce scalabitly and maintainability of your project.