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:

• "text-font": Overrides the font stack specified by the root layout property.
• "text-color": Overrides the color specified by the root paint property.
• "font-scale": Applies a scaling factor on text-size as specified by the root layout property.

Returns an image type for use in icon-image, *-pattern entries and as a section in the format expression. If set, the image argument will check that the requested image exists in the style and will return either the resolved image name or null, depending on whether or not the image 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.

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 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. 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.

Gets 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.

Gets the feature's geometry type: Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon.

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

Gets the progress along a gradient line. Can only be used in the line-gradient property.

Gets 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 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.

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.

Gets the length of an array or string.

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 non-null value is obtained, and returns that value.

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

• a single literal value; or
• an array of literal values, whose values must be all strings or all numbers (e.g. [100, 101] or ["c", "b"]). The input matches if any of the values in the array matches, similar to the "in" operator. Each label must be unique. 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:

• Point: Returns false if a point is on the boundary or falls outside the boundary.
• LineString: Returns false if any part of a line falls outside the boundary, the line intersects the boundary, or a line's endpoint is on the boundary.

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:

• ["linear"]: Interpolates linearly between the pair of stops just less than and just greater than the input.
• ["exponential", base]: Interpolates exponentially between the stops just less than and just greater than the input. base controls the rate at which the output increases: higher values make the output increase more towards the high end of the range. With values close to 1 the output increases linearly.
• ["cubic-bezier", x1, y1, x2, y2]: Interpolates using the cubic bezier curve defined by the given control points.

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 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 red, green, blue, and alpha components, in that order.

For two inputs, returns the result of subtracting the second input from the first. For a single input, returns the result of subtracting it from 0.

Returns the product of the inputs.

Returns the result of floating point division of the first input by the second.

Returns the remainder after integer division of the first input by the second.

Returns the result of raising the first input to the power specified by the second.

Returns the sum of the inputs.

Returns the absolute value of the input.

Returns the arccosine of the input.

Returns the arcsine of the input.

Returns the arctangent of the input.

Returns the smallest integer that is greater than or equal to the input.

Returns the cosine of the input.

Returns the shortest distance in meters between the evaluated feature and the input geometry. The input value can be a valid GeoJSON of type Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon, Feature, or FeatureCollection. Distance values returned may vary in precision due to loss in precision from encoding geometries, particularly below zoom level 13.

Returns the mathematical constant e.

Returns the largest integer that is less than or equal to the input.

Returns the natural logarithm of the input.

Returns mathematical constant ln(2).

Returns the base-ten logarithm of the input.

Returns the base-two logarithm of the input.

Returns the maximum value of the inputs.

Returns the minimum value of the inputs.

Returns the mathematical constant pi.

Rounds the input to the nearest integer. Halfway values are rounded away from zero. For example, ["round", -1.5] evaluates to -2.

Returns the sine of the input.

Returns the square root of the input.

Returns the tangent of the input.

Gets the current zoom level. Note that in style layout and paint properties, ["zoom"] may only appear as the input to a top-level "step" or "interpolate" expression.

Gets the kernel density estimation of a pixel in a heatmap layer, which is a relative measure of how many data points are crowded around a particular pixel. Can only be used in the heatmap-color property.