Basic filters

Operators

Unary operators

The following unary operators are supported: !, +, -

Usage example:

-(.user.birth.year - 1990)

Binary operators

The following binary operators are supported: +, -, /, *, +, <, >, %, <=, >=, ==, !=, ||, &&

Usage example:

3 + 1 == 4 * 1

The following Python-style operators are also available as an alternative:

or, and

Ternary operator (conditional)

The ternary (conditional) operator is the only emuto operator that takes three operands. The ternary operator is the equivalent of the if statement in other languages.

"Foo" if 3 < 4 else "Bar"  // "Foo"

3.14 if true == false else [42]  // [42]

Spread operator

The spread operator ... allows an iterable (like an array or string) to be expanded where zero or more elements are expected:

[1, 2, ...[3, 4], 5]

Identity $

Takes an input and returns it unchanged.

Property access .foo, .foo.bar

Retrieves a certain property of the input.

.foo.bar is equivalent to .foo | .bar

Property access can be made optional using a ?:

$?.foo?.bar

The effect of this is that when the left hand side of ?. is undefined or null, no error will be thrown. Instead, null will be returned.

This code does not produce an error:

{"foo": 4}?.bar?.foo

Projection $[3], $[0, -1], $["foo", "bar"]

Retrieve a single element from an object or array, or retrieve a list of elements.

When the projection has a single element (e. g. $["name"]) that property is returned.

In any other case, a list of each requested element is returned.

Just like with property access, optional chaining can be used with projection too. In this example, no error is produced. Instead, a null is returned.

null ?[3, 4]