04 / MAKING DECISIONS · LESSON 14

Repeat the useful part

Use a loop to calculate a running total.

10 min · learn at your pace

Work through a collection

A foreach statement assigns each item to a variable and runs a block:

foreach ($name in @('WEB-01', 'DB-01')) {
    "Checking $name"
}

A for loop is useful when you need an index or counter. Its three parts initialise the counter, test a condition, and update the counter.

for ($i = 0; $i -lt 3; $i++) {
    $i
}

Keep a running total

+= adds a value to a variable. Initialise the total before the loop, then output it after the loop finishes.

$total = 0
foreach ($number in 1..3) {
    $total += $number
}
$total

1..3 produces the range 1, 2, 3. ForEach-Object is another way to process each item, specifically in a pipeline. Although the names are similar, it is a cmdlet rather than the foreach language statement.

Use Stop if you accidentally write a loop that never ends. The lab also limits each execution to 30 seconds.

Try an example.ps1

foreach ($name in @('WEB-01', 'DB-01')) {
    "Checking $name"
}

YOUR TURN

Put it into practice.

Add the numbers 1 through 5 and output one total after the loop finishes.

See an explained solution

One way to solve it.ps1

$total = 0
foreach ($number in 1..5) {
    $total += $number
}
$total

The loop accumulates 1+2+3+4+5. Outputting only after the loop produces one result, 15.