Type Checking

The is operator tests whether a value is of a given type at runtime. The is not form negates the test.

value is number               # true if value is a number
value is not string            # true if value is NOT a string

Valid Type Keywords

number, string, boolean, array, object, null

Examples

if Data.input is number then
    Data.result = Data.input * 2
elseif Data.input is string then
    Data.result = ToUpper(Data.input)
end

Type checking is commonly used for input validation and type-safe processing:

if Data.items is null or Data.items is not array then
    fail "Items must be an array"
end

foreach item in Data.items do
    if item is not object then
        continue
    end
    if item.price is not number then
        continue
    end
    # Safe to process
end

Runtime Function

The TypeOf() standard library function returns the type name as a string:

TypeOf(42)        # "number"
TypeOf("hello")   # "string"
TypeOf(true)      # "boolean"
TypeOf([1, 2])    # "array"
TypeOf({a: 1})    # "object"
TypeOf(null)      # "null"