composableisValidate.js

// It's composable

const compose = (a,b) => v => a(b(v))
const isValid = valid => fn => (...p) => valid(...p) && fn(...p)

const hasTwoParams = isValid((...params) => params.length === 2)
const firstParamIsArray = isValid(a => Array.isArray(a))
const hasTwoFirstArray = compose(hasTwoParams, firstParamIsArray)
const myValidatedFn = hasTwoFirstArray((a, b) => console.log('It worked', a, b))

myValidatedFn([1,2,3], 'something') // It worked [ 1, 2, 3 ] something
myValidatedFn([1,2,3], 'something', 'bad') // false
myValidatedFn('bad', 'something') // false
myValidatedFn() // false
myValidatedFn('bad') // false

isValid.js

// higher order validation creator
const isValid = valid => fn => (...p) => valid(...p) && fn(...p)

// Example:

// Create a specific validation higher order function
const hasValidArrayOfObjects = isValid(data => {
  if (data // is there data
      && Array.isArray(data) // is data an array
      && data.length // is it not empty
      && typeof data[0] == 'object' // does it contain objects
      && !Array.isArray(data[0]) // is it a real object (not an array)
      && Object.keys(data[0]).length // does it have keys
  ) {
    return true
  }
  // Throw an error
  throw new Error('Invalid parameter. Expected an Array of objects')
})

// Use the validation fn above to create a safe function
const safelyExtractKeys = hasValidArrayOfObjects(data => Object.keys(data[0]))

// Use the safe function
safelyExtractKeys([{name:'smithy', status: 'offline'}]) // ['name', 'status']

safelyExtractKeys() // Throws an Error
safelyExtractKeys({}) // Throws an Error
safelyExtractKeys([{}]) // Throws an Error
safelyExtractKeys(123) // Throws an Error
safelyExtractKeys('thing') // Throws an Error
safelyExtractKeys([1,2,3]) // Throws an Error