JavascriptInterview

Javascript Interview Tricky Questions

Reverse the case of character eg lower to upper.

Example : reverseUpper("HEllO woRLd");

function reverseUpper(str){
     return str.split("").map(item=>item==item.toLowerCase() ? item.toUpperCase() : item.toLowerCase();
}

Reverse the string without inbuild function

function reverse(str){
let strs = "";
for(var x = str.length-1; x>0; x--){
strs+= str[x];
}
return strs;
}

Reverse the array without inbuild function

function reverseArrayInPlace(arr) {
  for (var i = 0; i <= Math.floor((arr.length - 1) / 2); i++) {
      let el = arr[i];
      arr[i] = arr[arr.length - 1 - i];
      arr[arr.length - 1 - i] = el;
  }
  return arr;
}

Balance Bracket

var checkBracket = function(str){
let stack = [];
let dict = {
'(':')',
'{':'}',
'[':']'
}

for(let i=0; i<str.length; i++){
if(str[i]==='(' || str[i] === '{' || str[i] === '[') {
stack.push(str[i]);
} else {
let end = stack.pop();
if(str[i]!==dict[end]) {
return false;
}

}

}
if(stack.length !==0) {
return false;
}
return true;


}

Find Duplicate values from multiple arrays.

Example : duplicate(..ar1, ...ar2, ...ar3)

function dups(){
var obj = {};
var dupl = [];

if(arguments.length>0){
for(var index in arguments){
let arg = arguments[index]
for(var x=0; x<arg.length; x++){
if(!obj[arg[x]]){
obj[arg[x]] = arg[x]
} else {
dupl.push(arg[x])
}

}
}
}

return Object.values(dupl);
}

Find Palindrome String

Example : "HelloWorld" => false
"HelloolleH" => true

function isPalindrome (str){
return str.split("").reverse().join("")==str
}

Find Consecutive Character

function letterCount(str){
  var s= str.match(/([a-zA-Z])\1*/g)||[];
return s.map(function(itm){
  return [itm.charAt(0), itm.length];
});
}