Logical Functions

These functions provide convenient one-line methods for evaluating expressions. They include methods for checking for empty values, using if-else logic, and implementing switch-case statements among others.

Boolean - Decode - DefaultValue - IIf - IsEmpty - When

Boolean

Boolean( value ) -> Boolean

Attempts to convert the given non-boolean value to a boolean value. For example a string 'true' would become true.

Returns: Boolean

Example

// returns `true`
Boolean('true')

// returns `false`. A value of 1 would return `true`
Boolean(0)

// returns `false`
Boolean('hello')

Decode

Decode( expression, [compare1, return1, ...compareN, returnN]?, default? ) -> *

Evaluates an expression to a value and compares the result value with the value of subsequent parameters. If the expression evaluates to a matching value, it returns the subsequent parameter value. If no matches are found, then a default value may be provided. This is similar to a switch/case statement

Returns:

Example

// returns a meaningful value when a field contains coded values
var code = $feature.codedValue;
var decodedValue = Decode(code, 1, 'Residential', 2, 'Commercial', 3, 'Mixed', 'Other');

DefaultValue

DefaultValue( value, defaultValue? ) -> *

Returns a specified default value if an empty value is detected.

Returns:

Example

// If a feature has no value in the POP_2000 field
// then 'no data' is returned
DefaultValue($feature.POP_2000, 'no data')

IIf

IIf( condition, trueValue, falseValue ) -> *

Returns a given value if a conditional expression evaluates to true, and returns an alternate value if that condition evaluates to false.

Returns:

Example

// returns 'below' if the value is less than 1,000,000.
// if the value is more than 1,000,000, then returns 'above'
var population = $feature.POP_2007;
IIf(population < 1000000, 'below', 'above');

IsEmpty

IsEmpty( value ) -> Boolean

Returns true if the provided value is null or an empty string (e.g. ''). Returns false for all other cases, including empty arrays and dictionaries.

Returns: Boolean

Example

// Returns true
IsEmpty(null)

// Returns false
IsEmpty('hello world')

When

When( [expr1, result1, ...exprN, resultN], default ) -> *

Evaluates a series of conditional expressions until one evaluates to true.

Returns: *

Example

Reclassify a numeric field value to a generic ranking (string)

If all expressions are false, then 'n/a' is returned

var density = $feature.densityField;
var ranking = When(density < 50, 'low', density >=50 && density < 100, 'medium', density >= 100, 'high', 'n/a');