console.clear();

​

const isNumber = num => typeof num === 'number';

const isFinite = num => Number.isFinite(num);

const notNull = num => null !== num;

const isDefined = num => undefined !== num;

const notNaN = num => !Number.isNaN(num);

const gt = (n1, n2) => n1 > n2;

​

const conditions = [

  isNumber,

  isFinite,

  notNull,

  isDefined,

  notNaN

];

​

const calcAllConditions = num =>

  conditions

    .map(cond => cond(num))

    .reduce((acc, curr) => acc && curr, true);

​

const calculate = (price, minPrice) => {

  if (calcAllConditions(price)

    && calcAllConditions(minPrice)  

    && gt(price, minPrice)) {

    console.log('Correct price');

    return price;

  } else {

    throw new Error('Wrong price'); 

  }

}

​

// const somePrice = 1000;

// const someMinPrice = 999;

// console.log(calculate(somePrice, someMinPrice)); // => 1000

​

// const wrongPrice = 999;

// console.log(calculate(wrongPrice, someMinPrice)); // => error

​

// test suites for kids

const testFnPure = (fn, params, res) => fn(...params) === res;

const testFnWithTry = (fn, params, res = 'error') => {

  const tempResult = (() => {

    try {

      return fn(...params);

    } catch(e) {

      return 'error'

    };

  })();

  console.log(tempResult)

  return res === tempResult;

};

console.log(testFnPure(calculate, [1000, 999], 1000)); // => true

console.log(testFnWithTry(calculate, [999, 999])); // => true

console.log(testFnWithTry(calculate, ['str', 999])); // => true

​

​