pxt-calliope/docs/reference/input/on-button-pressed.md
2016-04-13 08:27:45 -07:00

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# On Button Pressed
Register an [event handler](/reference/event-handler) that will execute whenever an input button (A, B, or A and B together) is pressed during program execution. When [running code](/js/simulator) with this function in a web browser, click an on-screen input button - labelled A or B.
```sig
input.onButtonPressed(Button.A, () => {})
```
### Example: count button clicks
This example counts how many times the left or right input button is pressed. Each time a button is pressed, the global count variable is increased by 1 and displayed on the screen.
```blocks
let count = 0
basic.showNumber(count)
input.onButtonPressed(Button.A, () => {
count++;
basic.showNumber(count);
})
```
### Example: roll a dice
This example generates a random number when you press the B input button, and then displays a random die image:
```blocks
input.onButtonPressed(Button.B, () => {
let dice = Math.random(6)
basic.showNumber(dice)
})
```
### Lessons
[smiley](/lessons/smiley), [answering machine](/lessons/answering-machine), [screen wipe](/lessons/screen-wipe), [rotation animation](/lessons/rotation-animation)
### See also
[button is pressed](/reference/input/button-is-pressed), [forever](/reference/basic/forever)