@chopinlang/helpers

Chopin Helpers

A collection of useful helper functions used internally in the Chopin compiler.

Installation

npm install @chopinlang/helpers

Usage

Include the object in your project:

const helpers = require("helpers");

// You can also destructure your assignment to only get the functions you need
const { isArray, isNumber, handleNegativeIndex } = require("helpers");

Functions

Array

arrayFrom

(object: any, [mapFn: (item: any, index: number, array: any[]) -> void, thisArg: any]) -> any[]

Returns an array from any object that can be converted to an array (e.g. an array-like object). Optional mapFn transforms every element of the array, and optional thisArg sets the context for mapFn.

first

(array: any[]) -> any

Returns the first item of an array.

isArray

(object: any) -> boolean

Determine if an object is an array.

isArrayLike

(object: any) -> boolean

Determine if an object is array-like, e.g. has a length property and items stored in numeric indexes.

last

(array: any[]) -> any

Returns the last item of an array.

toArray

(iterable: object[Symbol.iterator]) -> any[]

Converts an iterable object (array-like object) to an array.

Boolean

isBoolean

(value: any) -> boolean

Determine if a value is a boolean value.

Function

curry

(fn) -> fn

Auto-curry a function.

curryN

(length: number, fn) -> fn

Curry a function with specified arity of length.

curriedApply

(args: any[], fn) -> fn

Transform a function that takes multiple arguments into one that takes an array.

pipe

(val: any, fns: function[]) -> any

Pipe a value through a series of functions

pipeFns

(fns: ...function[]) -> function

Compose a series of functions from left-to-right.

withFunctionName

(name: string, fn) -> function

Add a name property to a function.

Null and Undefined

isNil

(value: any) -> boolean

Determine if a value is null or undefined.

isNull

(value: any) -> boolean

Determine if a value is specifically null.

isUndefined

(value: any) -> boolean

Determine if a value is specifically undefined.

nilDefault

(value: any, default: any) -> any

If a value is null or undefined, specify a default value to return. Otherwise, return the value itself.

Numeric

handleNegativeIndex

(index: number, seq: string|array|object) -> number

If second parameter is object, must be an array-like object or other iterable with numeric indexes.

Converts a negative index into its corresponding positive index relative to a sequence's length. Returns zero or positive index as-is.

isBigInt

(value: any) -> boolean

Determine if a value is a BigInteger.

isNumber

(value: any) -> number

Determine if a value is a number.

valueOf

(value: any) -> number

Convert a value into its numeric equivalent.

CAUTION: will return NaN if the value has no direct numeric equivalent. Will return Infinity or -Infinity if the value is too large or small to be represented by a JavaScript number.

Object

assign

(objects: object[]) -> object

Shallowly copies properties of each successive object to the first object in the order they are passed into the function. Mutates the first object.

callInternalToString

`(object: any) -> string

Calls Object.prototype.toString with object as the context.

classToString

(object: any) -> string

Gets the class or constructor name. Works with anonymous function expressions bound to variables, but the following returns an empty string:

let o = new (function () {})();

... so probably DON'T DO THAT.

clone

(object: any) -> any

Make a clone of an object. If the object has a clone method, it uses that. Otherwise, it recursively copies an object's own properties. Note that __proto__ is not an own property.

deepStrictEqual

(a: any, b: any) -> boolean

Recursively checks all properties of both objects for strict equality (===).

extend

(a: object, b: object) -> object

Copies b's properties shallowly onto a. Mutates a.

extendWithAll

(to: object, froms: object[]) -> object

Copies each property on every object in froms onto to. Goes from left-to-right, e.g. in case of conflicts a later argument's property will overwrite one from an earlier object. Mutates to.

forAllProperties

(object: any, fn: (property: any[, key: string, object: any]) -> void|boolean) -> void

Run fn callback on all own properties of any object. Breaks out of the loop if the callback returns false.

forEachProperty

(object: any, fn: (property: any[, key: string, object: any]) -> void|boolean) -> void

Run fn callback on the enumerable own properties of any object. Breaks out of the loop if the callback returns false.

getClass

(object: any) -> function

Get the constructor function or class used to create an object.

getOwn

(object: any, property: string) -> any

If an object has an own property, retrieve it. Otherwise returns false.

getProto

(object: any) -> any

Get the prototype of an object.

hasOwn

(object: any, property: string) -> boolean

Determine if an object has an own property.

hasProperty

(object: any, property: string) -> boolean

Determine if an object has a property anywhere in its prototype chain.

isObject

(value: any) -> boolean

Determine if a value is an instance of Object. Also detects objects with null prototypes.

isObjectType

(value: any) -> boolean

Determine if value typeof "object" is true.

mapObject

(object: object, fn: (any) -> any) -> object

Returns a new object with the same keys as the source object and a callback function applied to each of the source object's properties.

objectIs

(a: any, b: any) -> boolean

Checks if a and b are the exact same object. If primitive values and not NaN, checks for strict equality. Also correctly checks if NaN equals NaN.

ownPropertyNames

(object: any) -> string[]

Return an array of all an object's own string property names.

setAccessor

(target: object, key: string[, { getter: () -> any, setter: (...args: any) -> any }]) -> void

Sets a getter and setter (either or both optional) on target[key].

setProperty

(target: object, name: string, value: any[, enumerable: boolean|undefined, writable: boolean|undefined]) -> void

Sets a property and its attributes on a target object.

RegExp

isRegExp

(value: any) -> boolean

Determine if a value is a RegExp.

String

coerceToString

(value: any) -> string

If a value is not a string, coerce it to its string representation.

isString

(value: any) -> boolean

Determine if a value is a string.

trim

(string: string) -> string

Trims whitespace from both sides of a string.

Symbol

isSymbol

(value: any) -> boolean

Determine if a value is a Symbol.

Other Values

isDefined

(value: any) -> boolean

Determine if a value is defined.

Constants

__

Use as a placeholder for curry and curryN.