Library reference

Jolt ships with 79 built-in methods. Any of them can be called directly or piped with ->, and most accept either a JSON Path or a value. Range variables can be passed to nearly all of them.

Valid in says where a method can appear: in a property value, in a property name, as a statement inside a #using block, or as a case inside a #match.

Paths and existence

Method	Description	Valid in
`#exists`	Returns true if the provided value is not null, false otherwise.	Property value
`#isMissing`	Returns true if the provided path does not exist in the source document, false otherwise.	Property value
`#isNull`	Returns true if the provided value is null, false otherwise.	Property value
`#valueOf`	Gets the value of a property at the specified path.	Property value

Control flow

Method	Description	Valid in
`#eval`	Evaluates an arbitrary expression, either from a path or literal value, and returns the result. (unsafe)	Property name, Property value
`#if`	Evaluates one of two expressions depending on a boolean condition.	Property value
`#includeIf`	Includes the property’s object when a path or condition is true, and sets it to null otherwise.	Property name
`#try`	Evaluates an expression, and if it fails, evaluates a lambda with the exception and returns that result instead.	Property value

Loops and scoping

Method	Description	Valid in
`#foreach`	Loops over the elements of an array or the properties of an object, transforming each with a content template.	Property name
`#nameOf`	Returns the name of the property currently being iterated by a loop variable.	Property name
`#using`	Binds a path or value to a range variable so statements can modify it.	Property name

Statements

Method	Description	Valid in
`#removeAt`	Removes a JSON node at a variable-based path.	Statement
`#setAt`	Adds or modifies a JSON node at a variable-based path, creating missing parents.	Statement
`#when`	Executes one or more statements when a boolean expression is true.	Statement

Pattern matching

Method	Description	Valid in
`#default`	Always matches; use as the final catch-all case.	Match case
`#given`	Matches when an arbitrary boolean expression is true.	Match case
`#is`	Matches the value against a type, array pattern, object pattern, or scalar literal.	Match case
`#match`	Matches a value against cases from top to bottom and returns the value of the first one that matches.	Property name

Strings and arrays

Method	Description	Valid in
`#append`	Returns a string or array made by appending one or more strings or arrays.	Property value
`#contains`	Returns true when an array or string contains the provided value.	Property value
`#indexOf`	Returns the zero-based index of the first occurrence of the provided value.	Property value
`#length`	Returns the length of a string or array value.	Property value
`#reverse`	Returns the string or array with its elements in reverse order.	Property value

Strings

Method	Description	Valid in
`#endsWith`	Returns true if a string ends with the provided substring, false otherwise.	Property value
`#isRegexMatch`	Returns true if a string matches the provided regular expression, false otherwise.	Property value
`#joinWith`	Returns a string that joins all elements of an array with the provided delimiter.	Property name, Property value
`#regexReplace`	Returns the string with all matches of a regular expression replaced with another value.	Property value
`#replace`	Returns the string with all occurrences of a substring replaced with another value.	Property value
`#splitOn`	Returns an array of substrings by splitting a string on the provided delimiter.	Property value
`#startsWith`	Returns true if a string starts with the provided substring, false otherwise.	Property value
`#substring`	Returns the part of a string that falls within the provided range.	Property value
`#toLowerCase`	Returns the lowercase version of a string value.	Property value
`#toUpperCase`	Returns the uppercase version of a string value.	Property value
`#trim`	Returns the string with all leading and trailing whitespace removed.	Property value
`#trimEnd`	Returns the string with all trailing whitespace removed.	Property value
`#trimStart`	Returns the string with all leading whitespace removed.	Property value

Arrays and sequences

Method	Description	Valid in
`#any`	Returns true if an array or string has contents, or, with a lambda, if any element matches.	Property value
`#distinct`	Returns the items with distinct values of a specified property, or distinct scalar values.	Property value
`#flatten`	Returns a single array by recursively flattening an array of nested arrays.	Property value
`#orderBy`	Returns the array in ascending order of a selected value.	Property value
`#orderByDesc`	Returns the array in descending order of a selected value.	Property value
`#reduce`	Accumulates a single value by applying a two-parameter lambda to each element, with an optional seed.	Property value
`#select`	Returns an array of the results of projecting each element.	Property value
`#skip`	Returns the array without its leading elements, up to the specified count.	Property value
`#skipWhile`	Returns the array without the leading elements that satisfy a condition.	Property value
`#slice`	Returns the part of an array that falls within the provided range.	Property value
`#take`	Returns the leading elements of an array, up to the specified count.	Property value
`#takeWhile`	Returns the leading elements of an array that satisfy a condition.	Property value
`#where`	Returns the elements of an array that match a predicate.	Property value
`#zip`	Combines two arrays pairwise using a two-parameter lambda.	Property value

Grouping and aggregation

Method	Description	Valid in
`#average`	Returns the average of an array of numbers, optionally after a projection.	Property value
`#groupBy`	Groups an array’s elements by a selected value into key and results pairs.	Property value
`#max`	Returns the maximum of an array of numbers, optionally after a projection.	Property value
`#min`	Returns the minimum of an array of numbers, optionally after a projection.	Property value
`#sum`	Returns the total of an array of numbers, optionally after a projection.	Property value
`#summarizeWith`	Applies an aggregate expression to each group’s key and results.	Property value

Objects

Method	Description	Valid in
`#keysFrom`	Returns an array of the property names of an object.	Property value
`#merge`	Deep-copies and merges two or more objects, with later values taking precedence.	Property value
`#valuesFrom`	Returns an array of the property values of an object.	Property value

Numbers

Method	Description	Valid in
`#roundTo`	Returns a number rounded to the specified number of decimal places.	Property value

Dates and times

Method	Description	Valid in
`#addDays`	Returns an ISO 8601 date and time with the specified number of days added.	Property value
`#addHours`	Returns an ISO 8601 date and time with the specified number of hours added.	Property value
`#addMinutes`	Returns an ISO 8601 date and time with the specified number of minutes added.	Property value
`#currentDateTime`	Returns the current local date and time as an ISO 8601 string.	Property value
`#currentDateTimeUtc`	Returns the current UTC date and time as an ISO 8601 string.	Property value
`#formatDateTime`	Formats a date and time string using the provided format string.	Property value
`#parseDateTime`	Parses a string into an ISO 8601 date and time, requiring an exact format when one is given.	Property value

Types and conversion

Method	Description	Valid in
`#isArray`	Returns true if the value is an array, false otherwise.	Property value
`#isBoolean`	Returns true if the value is a boolean.	Property value
`#isDecimal`	Returns true if the value is a floating point number.	Property value
`#isEmpty`	Returns true if the value is an array or string with no contents, false otherwise.	Property value
`#isInteger`	Returns true if the value is a whole number.	Property value
`#isObject`	Returns true if the value is an object, false otherwise.	Property value
`#isString`	Returns true if the value is a string.	Property value
`#toBoolean`	Returns a value converted to a boolean.	Property value
`#toDecimal`	Returns a value converted to a floating point number.	Property value
`#toInteger`	Returns a value converted to a whole number.	Property value
`#toString`	Returns the string representation of a value.	Property value

Composition

Method	Description	Valid in
`#transformWith`	Transforms a sub-document with a registered, standalone transformer.	Property value

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