Asserts that the input is an array (optionally with a specific item type and length). If, when the input expression is evaluated, it is not of the asserted type, then this assertion will cause the whole expression to be aborted.

Asserts that the input value is a boolean. If multiple values are provided, each one is evaluated in order until a boolean is obtained. If none of the inputs are booleans, the expression is an error.

Returns a collator for use in locale-dependent comparison operations. The case-sensitive and diacritic-sensitive options default to false . The locale argument specifies the IETF language tag of the locale to use. If none is provided, the default locale is used. If the requested locale is not available, the collator will use a system-defined fallback locale. Use resolved-locale to test the results of locale fallback behavior.

Returns a formatted string for displaying mixed-format text in the text-field property. The input may contain a string literal or expression, including an 'image' expression. Strings may be followed by a style override object that supports the following properties:

Returns a ResolvedImage for use in icon-image , *-pattern entries, and as a section in the 'format' expression.

A 'coalesce' expression containing image expressions will evaluate to the first listed image that is currently in the style. This validation process is synchronous and requires the image to have been added to the style before requesting it in the 'image' argument.

Every image name can be followed by an optional ImageOptions object, which will be used for vector images only.

To implement crossfading between two images within a symbol layer using the icon-image-cross-fade attribute, include a second image as the second argument in the 'image' expression.

Provides a literal array or object value.

Asserts that the input value is a number. If multiple values are provided, each one is evaluated in order until a number is obtained. If none of the inputs are numbers, the expression is an error.

Converts the input number into a string representation using the providing formatting rules. If set, the locale argument specifies the locale to use, as a BCP 47 language tag. If set, the currency argument specifies an ISO 4217 code to use for currency-style formatting. If set, the unit argument specifies a simple ECMAScript unit to use for unit-style formatting. If set, the min-fraction-digits and max-fraction-digits arguments specify the minimum and maximum number of fractional digits to include.

Asserts that the input value is an object. If multiple values are provided, each one is evaluated in order until an object is obtained. If none of the inputs are objects, the expression is an error.

Asserts that the input value is a string. If multiple values are provided, each one is evaluated in order until a string is obtained. If none of the inputs are strings, the expression is an error.

Converts the input value to a boolean. The result is false when then input is an empty string, 0, false , null , or NaN ; otherwise it is true .

Converts the input value to a color. If multiple values are provided, each one is evaluated in order until the first successful conversion is obtained. If none of the inputs can be converted, the expression is an error.

Converts the input value to a number, if possible. If the input is null or false , the result is 0. If the input is true , the result is 1. If the input is a string, it is converted to a number as specified by the "ToNumber Applied to the String Type" algorithm of the ECMAScript Language Specification. If multiple values are provided, each one is evaluated in order until the first successful conversion is obtained. If none of the inputs can be converted, the expression is an error.

Converts the input value to a string. If the input is null , the result is "" . If the input is a boolean , the result is "true" or "false" . If the input is a number, it is converted to a string as specified by the "NumberToString" algorithm of the ECMAScript Language Specification. If the input is a color , it is converted to a string of the form "rgba(r,g,b,a)" , where r , g , and b are numerals ranging from 0 to 255, and a ranges from 0 to 1. If the input is an 'image' expression, 'to-string' returns the image name. Otherwise, the input is converted to a string in the format specified by the JSON.stringify function of the ECMAScript Language Specification.

Returns a string describing the type of the given value.

Returns the value of a cluster property accumulated so far. Can only be used in the clusterProperties option of a clustered GeoJSON source.

Retrieves a property value from the current feature's state. Returns null if the requested property is not present on the feature's state. A feature's state is not part of the GeoJSON or vector tile data, and must be set programmatically on each feature. Features are identified by their id attribute, which must be an integer or a string that can be cast to an integer. Note that ["feature-state"] can only be used with paint properties that support data-driven styling.

Returns the feature's geometry type: Point , LineString or Polygon . Multi* feature types return the singular forms.

Returns the feature's id, if it has one.

Returns the progress along a gradient line. Can only be used in the line-gradient and line-z-offset properties.

Returns the feature properties object. Note that in some cases, it may be more efficient to use ["get", "property_name"] directly.

Retrieves an item from an array.

Retrieves an item from an array. If the array contains numeric values and the provided index is non-integer, the expression returns an interpolated value between adjacent items.

Retrieves the configuration value for the given option. Returns null if the requested option is missing.

Retrieves a property value from the current feature's properties, or from another object if a second argument is provided. Returns null if the requested property is missing.

Tests for the presence of an property value in the current feature's properties, or from another object if a second argument is provided.

Determines whether an item exists in an array or a substring exists in a string. In the specific case when the second and third arguments are string literals, you must wrap at least one of them in a literal expression to hint correct interpretation to the type system .

Returns the first position at which an item can be found in an array or a substring can be found in a string, or -1 if the input cannot be found. Accepts an optional index from where to begin the search.

Returns the length of an array or string.

Returns a requested property of the light configuration based on the supplied options. Currently the only supported option is brightness which returns the global brightness value of the lights on a scale of 0 to 1, where 0 means total darkness and 1 means full brightness. This expression works only with 3D light, i.e. when lights root property is defined.

Returns an item from an array or a substring from a string from a specified start index, or between a start index and an end index if set. The return value is inclusive of the start index but not of the end index.

Logical negation. Returns true if the input is false , and false if the input is true .

Returns true if the input values are not equal, false otherwise. The comparison is strictly typed: values of different runtime types are always considered unequal. Cases where the types are known to be different at parse time are considered invalid and will produce a parse error. Accepts an optional collator argument to control locale-dependent string comparisons.

Returns true if the first input is strictly less than the second, false otherwise. The arguments are required to be either both strings or both numbers; if during evaluation they are not, expression evaluation produces an error. Cases where this constraint is known not to hold at parse time are considered in valid and will produce a parse error. Accepts an optional collator argument to control locale-dependent string comparisons.

Returns true if the first input is less than or equal to the second, false otherwise. The arguments are required to be either both strings or both numbers; if during evaluation they are not, expression evaluation produces an error. Cases where this constraint is known not to hold at parse time are considered in valid and will produce a parse error. Accepts an optional collator argument to control locale-dependent string comparisons.

Returns true if the input values are equal, false otherwise. The comparison is strictly typed: values of different runtime types are always considered unequal. Cases where the types are known to be different at parse time are considered invalid and will produce a parse error. Accepts an optional collator argument to control locale-dependent string comparisons.

Returns true if the first input is strictly greater than the second, false otherwise. The arguments are required to be either both strings or both numbers; if during evaluation they are not, expression evaluation produces an error. Cases where this constraint is known not to hold at parse time are considered in valid and will produce a parse error. Accepts an optional collator argument to control locale-dependent string comparisons.

Returns true if the first input is greater than or equal to the second, false otherwise. The arguments are required to be either both strings or both numbers; if during evaluation they are not, expression evaluation produces an error. Cases where this constraint is known not to hold at parse time are considered in valid and will produce a parse error. Accepts an optional collator argument to control locale-dependent string comparisons.

Returns true if all the inputs are true , false otherwise. The inputs are evaluated in order, and evaluation is short-circuiting: once an input expression evaluates to false , the result is false and no further input expressions are evaluated.

Returns true if any of the inputs are true , false otherwise. The inputs are evaluated in order, and evaluation is short-circuiting: once an input expression evaluates to true , the result is true and no further input expressions are evaluated.

Selects the first output whose corresponding test condition evaluates to true, or the fallback value otherwise.

Evaluates each expression in turn until the first valid value is obtained. Invalid values are null and 'image' expressions that are unavailable in the style. If all values are invalid, coalesce returns the first value listed.

Selects the output for which the label value matches the input value, or the fallback value if no match is found. The input can be any expression (for example, ["get", "building_type"] ). Each label must be unique, and must be either:

The input matches if any of the values in the array matches using strict equality, similar to the "in" operator. If the input type does not match the type of the labels, the result will be the fallback value.

Returns true if the evaluated feature is fully contained inside a boundary of the input geometry, false otherwise. The input value can be a valid GeoJSON of type Polygon , MultiPolygon , Feature , or FeatureCollection . Supported features for evaluation:

Produces continuous, smooth results by interpolating between pairs of input and output values ("stops"). The input may be any numeric expression (e.g., ["get", "population"] ). Stop inputs must be numeric literals in strictly ascending order. The output type must be number , array<number> , or color .

Interpolation types:

Produces continuous, smooth results by interpolating between pairs of input and output values ("stops"). Works like interpolate , but the output type must be color , and the interpolation is performed in the Hue-Chroma-Luminance color space.

Produces continuous, smooth results by interpolating between pairs of input and output values ("stops"). Works like interpolate , but the output type must be color , and the interpolation is performed in the CIELAB color space.

Produces discrete, stepped results by evaluating a piecewise-constant function defined by pairs of input and output values ("stops"). The input may be any numeric expression (e.g., ["get", "population"] ). Stop inputs must be numeric literals in strictly ascending order. Returns the output value of the stop just less than the input, or the first output if the input is less than the first stop.

Binds expressions to named variables, which can then be referenced in the result expression using ["var", "variable_name"].

References variable bound using "let".

Returns a string consisting of the concatenation of the inputs. Each input is converted to a string as if by to-string .

Returns the input string converted to lowercase. Follows the Unicode Default Case Conversion algorithm and the locale-insensitive case mappings in the Unicode Character Database.

Returns true if the input string is expected to render legibly. Returns false if the input string contains sections that cannot be rendered without potential loss of meaning (e.g. Indic scripts that require complex text shaping, or right-to-left scripts if the the mapbox-gl-rtl-text plugin is not in use in Mapbox GL JS).

Returns the IETF language tag of the locale being used by the provided collator . This can be used to determine the default system locale, or to determine if a requested locale was successfully loaded.

Returns the input string converted to uppercase. Follows the Unicode Default Case Conversion algorithm and the locale-insensitive case mappings in the Unicode Character Database.

Creates a color value from hue (range 0-360), saturation and lightness components (range 0-100), and an alpha component of 1. If any component is out of range, the expression is an error.

Creates a color value from hue (range 0-360), saturation and lightness components (range 0-100), and an alpha component (range 0-1). If any component is out of range, the expression is an error.

Creates a color value from red, green, and blue components, which must range between 0 and 255, and an alpha component of 1. If any component is out of range, the expression is an error.

Creates a color value from red, green, blue components, which must range between 0 and 255, and an alpha component which must range between 0 and 1. If any component is out of range, the expression is an error.

Returns a four-element array containing the input color's Hue, Saturation, Luminance and alpha components, in that order.

Returns a four-element array containing the input color's red, green, blue, and alpha components, in that order.