jsla-given

given-class.js

export default function given (val) {
  return Given(val)
}

class Given {
  constructor (value) {
    this._value = value
  }
  
  add (num) {
    this._value += num
    return this
  }

  subtract (num) {
    this._value -= num
    return this
  }

  multiply (num) {
    this._value *= num
    return this
  }

  divide (num) {
    this._value /= num
    return this
  }

  value () {
    return this._value
  }

  toString () {
    return `${this._value}`
  }

  valueOf () {
    return this.value()
  }
}

given-factory.js

export default function given (value) {
  const factory = {
    add: chainable(add),
    subtract: chainable(subtract),
    multiply: chainable(multiply),
    divide: chainable(divide),
    value: () => value
  }
  
  return factory

  function chainable(op) {
    return num => (value = op(value, num), factory)
  }
}

const add = (x, y) => x + y
const subtract = (x, y) => x - y
const multiply = (x, y) => x * y
const divide = (x, y) => x / y