On Start

An event that runs when the program starts.

let thousand = 1000

The on start is a special event that runs when the program starts, before any other event. Use this event to initialize your program.

In this example, on start sets a dimmer brightness on the screen and the button handler shows a string.

input.onButtonEvent(Button.A, input.buttonEventValue(ButtonEvent.Down), () => {
    basic.showString("Hello!")
})
led.setBrightness(50)

What about JavaScript?

Where is on start…?

function onStart(){} // I don't exist

on start only exists in the block editor. In JavaScript, all code executes sequentially starting at the first line.

When we transform the blocks into JavaScript, we always place all the event registrations (buttons, shake, …) before launching the on start code.

If a block from on start pauses, other registered events will have the opportunity to run as well.