Array Comprehensions

Array comprehensions build a new array from an existing collection in a single expression.

When to use it

Use a comprehension when you only need a simple mapping or filtering expression and want a concise result.

Syntax

LET squares = [FOR (n IN input.numbers) => n * n];
LET evens = [FOR (n IN input.numbers) IF n % 2 == 0 => n];

Example

TRANSFORM Tags {
    LET tags = [FOR (item IN input.items) => item.tag];
    OUTPUT { tags: tags };
}

Pitfalls

• Comprehensions allow only a single expression after =>.
• Use FOR EACH if you need multiple statements or side effects.

Try it

Open collection-transforms to see comprehensions alongside MAP/FILTER/REDUCE.

Related

• FOR EACH Loops
• Expressions