Expressions

Literals, string interpolation, and reading object properties and list elements.

An expression is anything that produces a value: a literal, a variable, a property or element access, an operator applied to other expressions, or a resource function call. Use parentheses to group expressions.

Object and list literals

Object literals list key: value pairs in curly braces. List literals list values in square brackets. Both can be nested and both allow a trailing comma.

request Literals {
    const car = {
        brand: "Honda",
        owner: { name: "Ana" },
        tags: ["compact", "hybrid"],
    }
    const colors = ["red", "green", "orange",]
    return car
}

• Object keys are bare identifiers. Quoted keys such as "brand": "Honda" aren’t supported.
• Keys must be unique within a single object literal.
• Values can be any expression, including variables and calculations: { total: price * quantity }.

String interpolation

Inside a string, ${expression} evaluates any expression and inserts the result:

request Interpolation {
    const name = "Ada"
    const items = 3
    return "Hello ${name}, you have ${items * 2} points"
    // "Hello Ada, you have 6 points"
}

Interpolated expressions can contain strings with their own interpolations: "a ${"b ${c}"}".

Values are rendered as follows:

Value	Rendered as
Numbers	Plain decimal notation, such as 42 or 0.3333333333
Booleans	true or false
null	null
Objects and lists	JSON, such as {"a":1,"b":[1,2]}

To include a literal ${ in a string, escape the dollar sign: "Price: \${amount}".

Reading object properties

Use dot notation to read a property:

request Properties {
    const car = { brand: "Honda", owner: { name: "Ana" } }
    return car.owner.name // "Ana"
}

• Reading a property that doesn’t exist returns null. It isn’t an error.
• Reading a property of anything other than an object, such as a string or null, is an error.

Because a missing property is null, you can check whether an object has a value with != null:

if (order.coupon != null) {
    // ...
}

Reading list elements

Use square brackets with a zero-based index to read a list element:

request Elements {
    const colors = ["red", "green", "orange"]
    return colors[1] // "green"
}

• The index must be an integer.
• An index outside the list is an error, for example List index 3 is out of bounds (list has 3 items).

Access can be chained: orders[0].items[2].price.

Not available

RequestScript is deliberately small. It has no built-in functions or methods, so there’s no way to get the length of a list or string, and no loops to iterate over a list. Logic that needs these is a good fit for a resource.