Type System

• Array
• Attachment
• Boolean
• Date
• Dictionary
• Feature
• FeatureSet
• FeatureSetCollection
• Geometry
• Number
• Text

Arcade has a full type system. It implicitly casts between types where appropriate, using a predefined set of rules.

Each type is described below.

Array

An object representing a list of elements. A single array can contain elements of various types, but they cannot have missing elements.

var z = [1,2,3];
var k = [1,2,"hello"];

return k[1];  // returns 2

z[0] = 23;  // z = [23,2,3]
z[3] = 24;  // Allowed as next sequential item;
z[1000] = 23 // Not allowed as would leave blanks;

You may iterate through the elements of an array using a for loop using the following syntax:

for (var index in myArray){
  // executes for each element in the array
}

Note that the variable index represents the index of the array, not the value of the element. So the following evaluates to 280:

var myArray = [10,20,30,40,50,60,70];
var sum = 0;
for(var k in myArray){
  sum += myArray[k];
}
// sum = 280
return sum;

Whereas the following slightly different code evaluates to 21:

var myArray = [10,20,30,40,50,60,70];
var sum = 0;
for(var k in myArray){
  sum += k;
}
// sum = 21
return sum;

Attachment

Defines information about attachments returned from feature service queries. These are fetched using the Attachments() function.

Boolean

Boolean values evaluate to either true or false.

var x = true;
var y = false;

String values resembling a boolean may be cast using the Boolean() function.

// z = true
var z = boolean('true');

Date

Dates describe a moment in time at various resolutions.

// Date only (no timestamp)
var x = Date(2007,11,1);  // December 1, 2007

// Date with timestamp
var n = Date(2008,11,1,12,55); // December 1, 2008 at 12:55 a.m.

Dictionary

A collection of key/value pairs. The keys of the dictionary are case insensitive.

var d = Dictionary("field1", 1, "field2",2);
return d.field1 + d["field2"];   // Can access elements with either notation


// Can also declare dictionaries using object notation.
var c = {
  "field1": 1,
  "field2": 2
}

Feature

Features have attributes and optionally a geometry.

var d = Feature(myGeometry, "field1", 1, "field2",2);
return d.field1 + d["field2"];   // Can access elements with either notation

return Geometry(d);  // Can get the geometry of the feature using the geometry function.

The Feature constructor is overloaded.

// Creating a Feature using a Dictionary
var feature = Feature(geom,  { "field1": 1, "field2": "myField2value" });

// You can also specify named parameters
var feature = Feature({ geometry: geom, attributes:   { "field1": 1, "field2": "myField2value" }  });

FeatureSet

A FeatureSet represents a connection to a set of Features in memory or in a server. FeatureSets are lazy, iterable, and chainable. FeatureSets allow you to access features from feature service layers within the map or feature service.

FeatureSets can be created from JSON with the FeatureSet() function, or referenced using the $layer global, which is a FeatureSet of all features in the same layer as the feature executing the Arcade.

// Returns the highest population among all features in the layer
Max($layer, "Population");

Or you can create a FeatureSet using one of the functions below, which takes the $map or $datastore as a global variable and returns one if its layers based on its title, layer ID, or portal item ID.

• FeatureSetById()
• FeatureSetByName()
• FeatureSetByPortalItem()

// returns true if the feature intersects sensitive land features from another layer in the map
var publicLandFeatures = FeatureSetByName($map, "public lands", ["class"], true);
var sensitiveAreas = Filter(publicLandFeatures, "class = 'sensitive'");
Count( Intersects( sensitiveAreas, $feature ) );

FeatureSetCollection

A collection of FeatureSets. This data type is only used when working with the $map and $datastore globals available in the Popup, Field Calculate, and Attribute Rule profiles. The $map represents a collection of layers (or FeatureSets) in the map of the feature executing the Arcade expression. The $datastore represents a collection of layers in the same feature service as the feature executing the Arcade expression.

For example, the FeatureSetByName() function returns the layer with the given name in the $map FeatureSetCollection.

var publicLandFeatures = FeatureSetByName($map, "public lands", ["class"], true);

Geometry

Arcade includes five geometry types: Point, Multipoint, Polyline, Polygon, Extent. Geometry is immutable, meaning it is not possible to change the geometry after it is created.

Features contain geometry, which may be returned from the Geometry() function.

// returns the feature's geometry
Geometry($feature)

// Geometry Types have overloaded functions.
var pt = Point({ 'x': 100, 'y': 100, 'spatialReference':{'wkid':102100} });
var polyline = Polyline({ 'paths' : [ [ [-97.06138,32.837], [-97.06133,32.836], [-97.06124,32.834], [-97.06127,32.832] ],  [ [-97.06326,32.759], [-97.06298,32.755] ] ] , 'spatialReference':{'wkid':102100}});
var poly = Polygon(Polygon({'rings' : [ [ [-97.06138,32.837], [-97.06133,32.836], [-97.06124,32.834], [-97.06127,32.832], [-97.06138,32.837] ],  [ [-97.06326,32.759], [-97.06298,32.755], [-97.06153,32.749], [-97.06326,32.759] ] ], 'spatialReference':{'wkid':102100}}));
var env = Extent({  'xmin' : -109.55, 'ymin' : 25.76, 'xmax' : -86.39, 'ymax' : 49.94, 'spatialReference':{'wkid':102100} });
var mp = Multipoint({ 'points' : [ [-97.06138,32.837], [-97.06133,32.836], [-97.06124,32.834], [-97.06127,32.832] ], 'spatialReference':{'wkid':102100} });

// General geometry creation. Will work out type from arguments.
var geom = Geometry({ 'x': 100, 'y': 100, 'spatialReference':{'wkid':102100} })

The following tables describe the specification of each geometry type.

Point

A point is a zero-dimensional geometry. This may be created by passing JSON in the format described below to the Point() function or by passing a point feature to the Geometry() function.

Multipoint

A multipoint is a zero-dimensional geometry. This may be created by passing JSON in the format described below to the Multipoint() function or by passing a multipoint feature to the Geometry() function.

Polyline

A polyline is a one-dimensional geometry. This may be created by passing JSON in the format described below to the Polyline() function or by passing a polyline feature to the Geometry() function.

Polygon

A polygon is a two-dimensional geometry. This may be created by passing JSON in the format described below to the Polygon() function or by passing a polygon feature to the Geometry() function.

Extent

An extent is a bounding box describing an area of interest. This may be created by passing JSON in the format described below to the Geometry().

Number

Numbers are a single data type that are used in computations and Math functions.

They can be integers.

var x = 10;
var y = 100;

Or floating point values.

var z = 1.2;
var n = Number("1.2");

String values resembling numbers may be cast using the Number() function.

// n = 1.2
var n = number("1.2");

Two number constants are also available for your convenience. Click the links below to see the documentation for each.

• Infinity
• PI

Text

The text type, also known as string, is a series of characters wrapped in single or double quotes. Any number or boolean may be converted to a text value using the Text() function.

var x = "This is a Text variable";
var z = 'This is also a text variable';

// n = "100"
var n = Text(100);

Several text constants are also available for your convenience. These allow you to insert special characters in text without needing to use escape characters. Click the links below to see the documentation for each.

• TextFormatting.BackwardSlash
• TextFormatting.DoubleQuote
• TextFormatting.ForwardSlash
• TextFormatting.NewLine
• TextFormatting.SingleQuote