Understanding of parseInt() funtion in JavaScript

parseInt() function in javascript is used to parse a string element and returns as an integer. 

Syntax:

It takes two parameters:

1. String: The string to be converted to an integer.
2. Radix (optional): An integer between 2 and 36 that represents the base of the numeral system used in the string. This is an optional parameter, and if not specified, JavaScript assumes the following:

• If the string begins with "0x" or "0X", it is parsed as a hexadecimal number. (Example is given at last). It is always better to specify by the programmers for clarity and understanding.

                                   Syntax: parseInt(String,radix) or parseInt(String) 

• Otherwise, it is parsed as a decimal number.

                                    Syntax: parseInt(String) 

 

Let us see the examples for a better understanding

Radix:

var num3="0x12345";

var num4="0X12345";

var num5="0123";

var num6="0012345";

console.log(parseInt(num3));

console.log(parseInt(num4));

console.log(parseInt(num5));

console.log(parseInt(num6));

The result will be 

74565

74565

123

12345

The conversion of hexadecimal to decimal numbers has been shown in the below image

Some examples of String

I initialize two variables as String. 

var number1="10";

var number2="20";

console.log("Type of number1 is "+typeof(number1));

console.log("Type of number2 is "+typeof(number2));

The result of the above code is

Type of number1 is string

Type of number2 is string

       

Example 1

When I try to add, it concatenates the values

//add two strings - concatenation

var total1=number1+number2;

console.log(`Total of two numbers is ${total1}`);

Result

Total of two numbers is 1020

 

Example 2

When I try to add two numbers by getting the values, the output would be NaN. Because 'value' is undefined and it is a string.

var total2=number1.value+number2.value;

console.log(`Total of two numbers is ${total2}`);

Result

Total of two numbers is NaN

  

Example 3

Use parseInt but add the numbers by getting the value of two numbers. Here also the output would be NaN. Because 'value' is undefined.

var total3=parseInt(number1.value)+parseInt(number2.value);

console.log(`Total of two numbers is ${total3}`);

Result

Total of two numbers is NaN

 

Example 4

Converting string to an integer using parseInt() function and adding the two integers

//converting string to integer and then adding the numbers

var total4=parseInt(number1)+parseInt(number2);

console.log(`Total of two numbers is ${total4}`);

The result would be the expected one

Total of two numbers is 30

Let me know your thoughts in the comments!