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

66 lines
1.5 KiB
Markdown
Raw Normal View History

2016-03-26 00:47:20 +01:00
# Forever
Repeat code [in the background](/microbit/reference/control/in-background) forever.
```sig
basic.forever(() => {
})
```
### Example: compass
The following example constantly checks the [compass heading](/microbit/reference/input/compass-heading) and updates the screen with the direction.
```blocks
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:
```blocks
let num = 0
basic.forever(() => {
basic.showNumber(num, 150)
})
input.onButtonPressed(Button.A, () => {
2016-03-26 00:47:20 +01:00
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:
```blocks
basic.forever(() => {
basic.showNumber(6789, 150)
})
input.onButtonPressed(Button.A, () => {
basic.showNumber(2, 150)
})
```
### Lessons
[blink](/microbit/lessons/blink), [bounce-image](/microbit/lessons/bounce-image), [snowflake-fall](/microbit/lessons/snowflake-fall), [flashing-heart](/microbit/lessons/flashing-heart)
### See also
[while](/microbit/js/while), [on button pressed](/microbit/reference/input/on-button-pressed), [in background](/microbit/reference/control/in-background)