Tiny Predicates

A collection of point-free predicate functions.

Predicates

• isNil: check if value is undefined or null
• isArray: point-free implementation of Array.isArray
• isInteger: point-free implementation of Number.isInteger
• isNumber: check if value is a Number primitive
• isObject: check if value is Object primitive
• isRegexp: check if value is a regular expression
• isString: check if value is a String primitive
• isFunction: check if value is a Function (including async and generator functions)
• isEmpty: check if a value is "empty" (e.g. [], {}, '', etc)

Usage

import { isArray, isNumber, isFunction } from '@earthtone/tiny-predicates'

const string = 'this is a list of characters, but not actually an array'
const characters = ['f', 0, 0, 'b', 4, 'r']

function doSomething (list) {
  if (!isArray(list)) return list
  list.map(x => {
    if (!isNumber(x)) return x
    else x + 10
  })
}

console.log(doSomething(string)) // -> 'this is a list of characters, but not actually an array'
console.log(doSomething(characters).join('')) // -> 'f1010b14r'

function anyArgs (...args) {
  if (isFunction(args[0]) && isArray(args[1])) {
    return args[1].map(args[0])
  } else if (isFunction(args[1]) && isArray(args[0])) {
    return args[0].map(args[1])
  } else {
    throw new Error('I need an Array and a Callback!')
  }
}

console.log(anyArgs(x => x * 10, [1, 2, 3]) // -> [10, 20, 30]
console.log(anyArgs([2, 4, 6], x => x * 10) // -> [20, 40, 60]
console.log(anyArgs('foo', 100) // -> Error!

Note

isEmpty leverages utility functions included in the Ramda library, but unlike Ramda's implementation, it does not support Typed Arrays.