pxt-calliope/docs/reference/input/on-button-pressed.md

On Button Pressed

Start an event handler (part of the program that will run when something happens, like when a button is pressed). This handler works when button A or B is pressed, or A and B together. When you are using this function in a web browser, click the buttons on the screen instead of the ones on the @boardname@.

input.onButtonPressed(Button.A, () => {})

Example: count button clicks

This example counts how many times you press the A button. Each time you press the button, the LED screen shows the count variable getting bigger.

let count = 0
basic.showNumber(count)
input.onButtonPressed(Button.A, () => {
    count++;
    basic.showNumber(count);
})

Example: roll dice

This example shows a number from 1 to 6 when you press the B button.

input.onButtonPressed(Button.B, () => {
    let dice = Math.random(6) + 1
    basic.showNumber(dice)
})

~hint

This program adds a 1 to random(6) so the numbers on the dice will come out right. Otherwise, sometimes they would show a 0.

~

See also

button is pressed, forever, random