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Repeat code a preset number of times.

@parent js/language

Repeat code a fixed number of times.

Block Editor

The Block Editor for loop is different than the Touch Develop for loop in an important way. The above for loop will iterate five times, with the loop variable i taking on values 0, 1, 2, 3, and 4. The Touch Develop for loop shown below will iterate four times:

for (let k = 0; k < 4; k++) {
}

Touch Develop

~hide

let upper = 5

~

for (let k1 = 0; k1 < upper; k1++) {
    // Add code to repeat here, also called the `loop body`
}

where

0 is initial value of the loop index variable k
the value of k increases by 1 after each execution of the loop body
upper is the number of times the loop body will repeat

In other words, the index variable (k) starts at 0 and increases by 1 each time the loop body executes, until k = upper.

Example: count to 5

The following example displays numbers 1 through 5 on the LED screen:

for (let i = 0; i < 5; i++) {
    basic.showNumber(i + 1, 100)
    basic.pause(500)
}

Example: draw a box

The LED screen has a fixed number of rows and columns (5x5), which is ideal for a for loop. This example uses a for loop to turn on the LEDs along the edge of the screen, making a square.

for (let i1 = 0; i1 < 5; i1++) {
    led.plot(0, i1)
    led.plot(4, i1)
    led.plot(i1, 0)
    led.plot(i1, 4)
    basic.pause(500)
}

~hint

Want to exit a loop early? The break statement exits a loop before the end value is reached.

~

Lessons

looper, strobe light

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