pxt-calliope/docs/reference/js/if.md
2016-03-25 16:47:20 -07:00

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# If
Run code based on a condition. #docs #if #then #else #endif #language #elseif
### @parent js/language
Conditionally run code depending on whether a [Boolean](/microbit/reference/types/boolean) condition is true or false.
### Block Editor
![](/static/mb/hourofcode-0.png)
In the Block Editor, click on the dark blue gear icon (see above) to add an *else* or *if* to the current block.
### Touch Develop
### ~hide
```
let condition = true
```
### ~
```
if (condition) {
// this code runs if `condition` is `true`
} else {
// this code runs if `condition` is `false`
}
```
### Example: adjusting screen brightness
If the screen [brightness](/microbit/reference/led/brightness) is `< 100`, this code sets the brightness to `255`:
```
if (led.brightness() < 100) {
led.setBrightness(255)
}
```
You can leave the `then` or `else` blocks empty if they aren't needed.
### Else if: multiple if statements
You can chain together if statements by using `else if`. Like this:
### ~hide
```
let otherCondition = true
```
### ~
```
if (condition) {
// this code runs if `condition` is `true`
} else if (otherCondition) {
// this code runs if `other condition` is `true`
}
else {
// this code runs if neither `condition` or `other condition` are `true`
}
```
### Example: compass heading
The following example gets the [compass heading](/microbit/reference/input/compass-heading) and then uses ``if-then-else`` statements to display a letter on the screen (N for north, E for East, S for South, and W for West).
```
while (true) {
let degrees = input.compassHeading()
if (degrees < 45) {
basic.showString("N", 100)
} else if (degrees < 135) {
basic.showString("E", 100)
}
else if (degrees < 225) {
basic.showString("S", 100)
}
else {
basic.showString("W", 100)
}
}
```
### Drag and drop
You can move an entire ``if`` block by clicking the ``if`` keyword and dragging and dropping.
### Lessons
[love meter](/microbit/lessons/love-meter), [zoomer](/microbit/lessons/zoomer), [offset image](/microbit/lessons/offset-image)
### See also
[while loop](/microbit/js/while), [for](/microbit/reference/loops/for), [boolean](/microbit/reference/types/boolean)