pxt-calliope/docs/reference/basic/forever.md

Forever

Repeat code in the background forever.

basic.forever(() => {
})

Example: compass

The following example constantly checks the compass heading and updates the screen with the direction.

basic.forever(() => {
    let heading = input.compassHeading()
    if (heading < 45) {
        basic.showString("N", 100)
    } else if (heading < 135) {
        basic.showString("E", 100)
    }
    else if (heading < 225) {
        basic.showString("S", 100)
    }
    else {
        basic.showString("W", 100)
    }
})

Example: counter

The following example continually shows the current value of a global variable:

let num = 0
basic.forever(() => {
    basic.showNumber(num, 150)
})
input.onButtonPressed(Button.A, () => {
    num = num + 1
})

Contention for the LED display

If you have multiple processes that each show something on the LED screen, you may get unexpected results. Try, for example:

basic.forever(() => {
    basic.showNumber(6789, 150)
})
input.onButtonPressed(Button.A, () => {
    basic.showNumber(2, 150)
})

Lessons

blink, bounce-image, snowflake-fall, flashing-heart

See also

while, on button pressed, in background