[2021] Top 10 Javascript Advanced & Programming Interview Questions and Answers

1. Explain the difference between Object.freeze(), Object.seal() and Const ?

2. Explain prototype in Javascript with example (s).

3. What is the difference between ES5 and ES6 and what needs to programmatically changed ?

4. Difference between function declaration and function ?

5. What is Arrow function ?

6. Can we able to use the typeof to check the array ?

No, typeof “[]” also returns “object” only.

So to check whether the given value is array or not need to use Array.isArray()

var input = [1 , 2, 3];
if(typeof(input) == 'object'){
console.log("this is object");
}

// where as the below prints tru
Array.isArray(input); // prints true as input is array.

7. How do you divide the given array into 2 parts in javascript ?

Lets consider the given size is of length even, then

var array = [1, 2, 3, 4, 5, 6]; 
var length = array.length;
var array2= array.splice(length/2, length);
var array1= array.splice(0, length/2);
console.log(array1); // (3) [1, 2, 3]
console.log(array2); // (3) [4, 5, 6]

If your given array is odd length then,

var array = [1, 2, 3, 4, 5, 6,7]; 
var length = array.length;
var array2= array.splice(length/2, length);
var array1= array.splice(0, length/2);
console.log(array1); // (3) [1, 2, 3]
console.log(array2); // (3) [4, 5, 6, 7]

8. How do you divide the array into given size equally in javascript ?

var array = [1, 2, 3, 4, 5, 6,7,8,9,10,11,12,13,14,15]; 
var splitSize = 3;
var arraySize = array.length;
var temp = 0;
for(let i=0;i < arraySize;i++){
temp++;
if(splitSize == temp){
temp =0;
var newArray = array.splice(0, splitSize);
console.log(newArray);
}
}
// prints
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]
[10, 11, 12]

We have another way as well

let inputArray = [1,2,3,4,5,6,7,8,9];
let splitCount = 3;
let outputArray = [];
for (let i=0;i<inputArray.length;i+=splitCount){	
	let tempArray = [];
	for(let j=i;j<splitCount+i;j++){
		tempArray.push(inputArray[j]);		
	}
	outputArray.push(tempArray);
}
console.log(outputArray);