interview-for-js.js

// Factorial
function factorial(n) {
  if(n === 0) {
    return 1;
  } else {
    return n * factorial(n-1);
  }
}
factorial(5) //= 120



//Closures
for (var i = 0; i < 5; i++) {
  var btn = document.createElement('button');
  btn.appendChild(document.createTextNode('Button ' + i));
  btn.addEventListener(
    'click', 
    //---------------
      (function(e) {
        return function() {
            console.log(e);
        }
      })(i)
    //---------------
  );
  document.body.appendChild(btn);
}
// If you don't use closures , after click on button you will see always "5"


//Clone obj in jacascript
var dog = {height: 34,speed: 45},
    cat = {old: 45,ololo : 34};
  
  //first way
  function cloneObj(inbox, outbox){
    for (prop in outbox) {
      inbox[prop] = outbox[prop];
    }
    return inbox
  }
  
  //second way
  function cloneObj(data1 , data2){
    return Object.assign({}, arguments);  
  }
  
  
  

//Array Flatten
var arr = ["1",["2" ,"3", ["4","5"] , ["6" , ["7","8",["10"]]]]];

function flatten(arr) {
  var myArr = [];  
    
  for (var i = 0; i < arr.length; i++){
    if (Array.isArray(arr[i])) {
      myArr = myArr.concat(flatten(arr[i]));  
    } else {
      myArr.push(arr[i]);
    }
  }

  return myArr;   
}

console.log(flatten(arr))



// Find brackets
function findBrackets(str){
  var brackets = "{}[]()";
  var result = [];
  var position;
  
  for (var i = 0, max = str.split('').length; i < max; i++) {
    position = brackets.indexOf(str.split('')[i]);
    
    if (position > -1) {
      if (position % 2 === 0) {
        result.push(position + 1);
      } else if (result.pop() !== position) {
          return false;
      }      
    }
    
  }
  return result.length === 0;
}

console.log(findBrackets("(2+2)*{fgdfg/dfgh//}{{{}aaa"));
console.log(findBrackets("(2+2)*{fgdfg/dfgh//}{}aaa"));
console.log(findBrackets("(2+2())*{fgdfg/dfgh//}{}aaa"));
console.log(findBrackets("(2+2{)}*{fgdfg/dfgh//}{}aaa"));


//Diagonal ddifference
//Given a square matrix of size N×N, calculate the absolute difference between the sums of its diagonals.
var a = [
  [1,2,3,5],
  [1,5,9,5],
  [1,5,0,8],
  [9,5,0,5]
]


function diagonalsX() {
    var result = 0;
    a.forEach(function(item , i ,a) {
      result = result + item[i];
    })        
    
    return result;
}

function diagonalsY() {
    var result = 0;
    a.forEach(function(item , i ,a) {
      result = result + item[item.length - (i+1)]; 
    })        
    
    return result;
}
    
console.log(Math.abs(diagonalsX() - diagonalsY())); 



// Is palindrome 
var str = 'lool';
[].map.call(str, function(x) {
  return x;
}).reverse().join('');
  

take a look for Object.create() func in spec. At least it will actually clone object instead of copying properties.

Thanks , I will add this way.