pxt-calliope/olddocs/js/if.md

If

Run code based on a condition.

@parent javascript/language

Conditionally run code depending on whether a Boolean condition is true or false.

Block Editor

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 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 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, zoomer, offset image

See also

while loop, for, boolean