hFunction.js

    function countdown(num) {
        let startNumber = num;
        let fn = function () {
          startNumber--;
          if (startNumber === 0) {
            clearInterval(timerId);
            console.log("DONE!");
          } else {
            console.log(startNumber);
          }
        };
    
        let timerId = setInterval(fn, 1000);
      }
    //   countdown (5);
    
      //2 
      function randomGame(){
    
        function counter(){
          let count = 0;
          return function(){
              return ++count
          }
        }
        let gameCount = counter();
    
        function fn(){
          var randomNum = Math.random();
          if(randomNum > 0.75){
            console.log(gameCount());
              clearInterval(timerId);
          } else {
            gameCount()
          }
        }
        let  timerId = setInterval(fn, 1000);
      }
        // console.log(randomGame())
      //3
      function isEven(num) {
        return num % 2 === 0 ? true : false;
      }
    //   console.log(isEven (2))
    
      //4
      function isOdd(num) {
        return num % 2 !== 0 ? true : false;
      }
    //   console.log(isOdd (14))
    
      //5
      function isPrime(n){
    
        for (let i = 2; i <= Math.sqrt(n); i++) {
          if(n % i === 0){
            return false;
          }
        };
    
        if(n !== Math.round(n)){
          return false;
        } else if(n < 2){
          return false;
        } else {
          return true;
        }
      }
    //   console.log(isPrime(8))
    
      //6
      function numberFact(num,callback){
      return callback(num)
      }
    //   console.log(numberFact(59, isEven))
    
        //7
        function find (array, callback){
      return array.find (function (value){
          if (callback(value))
          return value
      })
        }
        let result = find ([8,11,4,27], function(val){
        return val >= 10
        })
    //  console.log (result)
    
        //8
      function findIndex (array, callback){
        return array.findIndex (function (value){
          if (callback(value))
          return value
        })
      }
    //     let result = findIndex ([8,11,4,27], function(val){
    //   return  val >= 10
    //     })
    //     console.log (result)
    
      //9
      function specialMultiply(a,b){
        if(arguments.length === 1){
          return function(b){
            return a*b;
          }
        }
        return a*b;
      }
    //   console.log(specialMultiply(3,4)) // 12
    //   console.log(specialMultiply(3)(4)); // 12
    //   console.log(specialMultiply(3));