DEV Community: Asikur Rahman

10 Javascript interview questions that will help you taking preparation

Asikur Rahman — Sat, 08 May 2021 11:16:02 +0000

What is the difference between null and undefined?
Answer: Null means to cancel out something or not the existence of something that means if we set a variable null, we can say that there is nothing in the variable.
But undefined can happen in many ways if we want to access a parameter that is not passed then we get undefined if we just declare a variable without values then it will show undefined if we want to access a property of an object which is not present there that will also give us undefined.
this will be enough to explore that you know something about that question.
Difference between double equal(==) and triple equal(===)?
Answer: Triple equal is very strict it will show the type of variable that is compared but double equal is not so strict it will convert the variable into the same type and then check. For example:

All you need to know about ReactJs as a beginner.

Asikur Rahman — Fri, 07 May 2021 14:09:59 +0000

React is the most popular Javascript library nowadays. So there is a huge number of interested developers who want to learn React. In this article I'll tell you a little information what you have to know as a beginner React developer.
To be continued....

How to make Javascript code neat and clean

Asikur Rahman — Thu, 06 May 2021 12:24:46 +0000

Curly Braces
If there is a block then we use curly braces. We should use a space before the bracket like this:

So do we have to use curly braces if there is one conditional line?

Well, using curly braces is safe and good practice but you can write without a curly brace if there is only one line in the condition.

Line length
No one likes to read along the horizontal line it’s better to split them into small lines.

Indents
There are two types of indents
Horizontal indents: 2 or 4 space
A horizontal indentation is made using either 2 or 4 spaces or the horizontal tab symbol(key Tab)

Vertical indents: empty line for splitting codes into logical blocks
Even a single function can often be divided into logical blocks.

Semicolons
A semicolon should be present after each statement, even if it could possibly be skipped.

There are languages where a semicolon is truly optional and it is rarely used. In JavaScript, though, there are cases where a line break is not interpreted as a semicolon, leaving the code vulnerable to errors.

Nesting level
Try to avoid nesting code too many levels deep.
For example, instead of adding a nested if/else we can use a return conditional like this:
Option-1:

Option-2:

Function placement
The most preferable method is code first then function

Summary
The main point of this writing is to make code readable. We should concern about that is our code readable and easy to understand.
We can read popular style guides to keep up to date about coding style trends and best practice.

10 facts about Javascript

Asikur Rahman — Wed, 05 May 2021 13:57:42 +0000

1.Character access in string
There are two way to access characters of the string, one is using charAt()

The other way is just like an array-like object to access each character of the string.

2.Find the index of string
By using the indexOf() function we can easily find the first matching index number of a string. This function mainly return the index of the first matching string.

3.Changing the case of a string.
If we want to convert an upper case letter into a lower case then we dont have to convert it by using ASCII value like in C. Javascript has two beautiful function to do that toUpperCase() convert lower case letter into upper case and toLowerCase() do the reverse of toUpperCase().

4.String to integer/float
There are two functions in javascript which allow us to parse a string into an integer or float in one second which is parseInt() and parseFloat().
parseInt() take two parameters first one is the string and the second one is the base of the number system while parseFloat() do it for only the decimal number system and take only one parameter.

Random numbers in javascript Math.random() return a floating number range from 0 to less than 1. So if we want any fixed ranged random number than we have to multiply Math.random() with what we want. Suppose if we want a random number from 1 to 6 than we can do this

6.Loop over an array
If we want to access each element of an array then we can use forEach() loop which is much easier and shorter than for loop.

7.Inserting element and removing element from the array
Using push() we can insert a new element in the array and by pop() we can remove the last element from the array

8.Difference between find() and filter()
By using filter() we get a portion of that array but using find() we get an element.

9.Difference between slice() and splice()
The slice() method returns the selected items as a new array object and don’t change the original array while splice() method returns the original array with removed items.

Difference between shift() and unshift() The shift() method remove an element at a specific position and shifts the remaining elements up while returns the removing element In the meantime unshift() exactly done the opposite thing it adds an element at a specific position and shifts the remaining element down and return the size of the array.