Class Functions

A class that contains the built-in JMESPath functions.

The built-in functions are implemented as methods on the Functions class. Each method is decorated with the @Function.signature() decorator to enforce the arity and types of the arguments passed to the function at runtime.

You can extend the Functions class to add custom functions by creating a new class that extends Functions and adding new methods to it.

Example

import { search } from '@aws-lambda-powertools/jmespath';
import { Functions } from '@aws-lambda-powertools/jmespath/functions';

class MyFunctions extends Functions {
  ⁣@Functions.signature({
    argumentsSpecs: [['number'], ['number']],
    variadic: true,
  })
  public funcMyMethod(args: Array<number>): unknown {
    // ...
  }
}

const myFunctions = new MyFunctions();

search('myMethod(@)', {}, { customFunctions: new MyFunctions() });

Hierarchy (View Summary)

Constructors

constructor

Properties

methods

Methods

funcAbs funcAvg funcCeil funcContains funcEndsWith funcFloor funcJoin funcKeys funcLength funcMap funcMax funcMaxBy funcMerge funcMin funcMinBy funcNotNull funcReverse funcSort funcSortBy funcStartsWith funcSum funcToArray funcToNumber funcToString funcType funcValues introspectMethods signature

Constructors

constructor

Properties

methods

methods: Set<string> = ...

A set of all the custom functions available in this and all child classes.

Methods

funcAbs

  • funcAbs(args: number): number

  • Get the absolute value of the provided number.

    Parameters

    • args: number

      The number to get the absolute value of

    Returns number

funcAvg

  • funcAvg(args: number[]): number

  • Calculate the average of the numbers in the provided array.

    Parameters

    • args: number[]

      The numbers to average

    Returns number

funcCeil

  • funcCeil(args: number): number

  • Get the ceiling of the provided number.

    Parameters

    • args: number

      The number to get the ceiling of

    Returns number

funcContains

  • funcContains(haystack: string, needle: string): boolean

  • Determine if the given value is contained in the provided array or string.

    Parameters

    • haystack: string

      The array or string to check

    • needle: string

      The value to check for

    Returns boolean

funcEndsWith

  • funcEndsWith(str: string, suffix: string): boolean

  • Determines if the provided string ends with the provided suffix.

    Parameters

    • str: string

      The string to check

    • suffix: string

      The suffix to check for

    Returns boolean

funcFloor

  • funcFloor(args: number): number

  • Get the floor of the provided number.

    Parameters

    • args: number

      The number to get the floor of

    Returns number

funcJoin

  • funcJoin(separator: string, items: string[]): string

  • Join the provided array into a single string.

    Parameters

    • separator: string

      The separator to use

    • items: string[]

      The array of itmes to join

    Returns string

funcKeys

funcLength

  • funcLength(arg: string | unknown[] | Record<string, unknown>): number

  • Get the number of items in the provided item.

    Parameters

    • arg: string | unknown[] | Record<string, unknown>

      The array to get the length of

    Returns number

funcMap

funcMax

  • funcMax(arg: (string | number)[]): null | string | number

  • Get the maximum value in the provided array.

    Parameters

    • arg: (string | number)[]

      The array to get the maximum value of

    Returns null | string | number

funcMaxBy

funcMerge

funcMin

  • funcMin(arg: number[]): null | string | number

  • Get the minimum value in the provided array.

    Parameters

    • arg: number[]

      The array to get the minimum value of

    Returns null | string | number

funcMinBy

funcNotNull

funcReverse

  • funcReverse(arg: string | unknown[]): string | unknown[]

  • Reverses the provided string or array.

    Parameters

    • arg: string | unknown[]

      The string or array to reverse

    Returns string | unknown[]

funcSort

  • funcSort(arg: string[] | number[]): unknown[]

  • Sort the provided array.

    Parameters

    • arg: string[] | number[]

      The array to sort

    Returns unknown[]

funcSortBy

funcStartsWith

  • funcStartsWith(str: string, prefix: string): boolean

  • Determines if the provided string starts with the provided prefix.

    Parameters

    • str: string

      The string to check

    • prefix: string

      The prefix to check for

    Returns boolean

funcSum

  • funcSum(args: number[]): number

  • Sum the provided numbers.

    Parameters

    • args: number[]

      The numbers to sum

    Returns number

funcToArray

funcToNumber

  • funcToNumber(arg: JSONValue): null | number

  • Convert the provided value to a number.

    If the provided value is a number, then it is returned. Otherwise, the value is converted to a number and returned.

    If the value cannot be converted to a number, then null is returned.

    Parameters

    • arg: JSONValue

      The value to convert to a number

    Returns null | number

funcToString

  • funcToString(arg: JSONValue): string

  • Convert the provided value to a string.

    If the provided value is a string, then it is returned. Otherwise, the value is converted to a string and returned.

    Parameters

    • arg: JSONValue

      The value to convert to a string

    Returns string

funcType

funcValues

introspectMethods

  • introspectMethods(scope?: Functions): Set<string>

  • Lazily introspects the methods of the class instance and all child classes to get the names of the methods that correspond to JMESPath functions.

    This method is used to get the names of the custom functions that are available in the class instance and all child classes. The names of the functions are used to create the custom function map that is passed to the JMESPath search function.

    The method traverses the inheritance chain going from the leaf class to the root class and stops when it reaches the Functions class, which is the root class.

    In doing so, it collects the names of the methods that start with func and adds them to the methods set. Finally, when the recursion collects back to the current instance, it adds the collected methods to the this.methods set so that they can be accessed later.

    Parameters

    • Optionalscope: Functions

      The scope of the class instance to introspect

    Returns Set<string>

Staticsignature

  • signature(options: FunctionSignatureOptions): FunctionSignatureDecorator

  • Decorator to enforce the signature of a function at runtime.

    The signature decorator enforces the arity and types of the arguments passed to a function at runtime. If the arguments do not match the expected arity or types errors are thrown.

    Parameters

    Returns FunctionSignatureDecorator

    Example

    import { PowertoolsFunctions } from '@aws-lambda-powertools/jmespath/functions';

    class MyFunctions extends Functions {
      ⁣@Functions.signature({
        argumentsSpecs: [['number'], ['number']],
        variadic: true,
      })
      public funcMyMethod(args: Array<number>): unknown {
        // ...
      }
    }

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