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