JavaScript Number parseInt() Method

The parseInt() method in JavaScript converts a string into an integer (a whole number) based on the specified radix (base). If the first character of the string cannot be converted to a number, NaN is returned.

The method takes two parameters: the string to be parsed and the radix (optional, default is 10).
2 = binary, 8 = octal, 10 = decimal, 16 = hexadecimal.

Number parseInt() Method Syntax

parseInt(Value, radix);

Number parseInt() Method Parameters

• Value: This parameter contains a string that is converted to an integer.
• radix: This parameter represents the radix or base to be used and it is optional.

Number parseInt() Method Return value

It returns a number and if the first character can’t be converted to a number then the function returns NaN. It returns a number parsed up to that point where it encounters a character that is not a number in the specified radix(base). 

Number parseInt() Method Examples

Example 1: Parsing float value

Here, we are using the parseInt() method to parse the given float value.

javascript

let v1 = parseInt("3.14");
console.log('Using parseInt("3.14") = '+ v1);

Output

Using parseInt("3.14") = 3

Explanation

• In the above example we parseInt(“3.14”) converts the string “3.14” to an integer.
• Since “3.14” is parsed, only the integer part (3) is considered.
• The value of v1 will be 3, not 3.14.

Example 2: Parsing value with given radix

Here, we will also mention radix with the number.

javascript

// Base 10
a = parseInt("100", 10);
console.log('parseInt("100",10) = ' +
    a);

// Base 8
b = parseInt("8", 8);
console.log('parseInt("8",8) = ' +
    b);

// Base 8
c = parseInt("15", 8);
console.log('parseInt("15",8) = ' +
    c);

// Base 16
d = parseInt("16", 16);
console.log('parseInt("16",16) = ' +
    d);

// Leading and trailing spaces are ignored
// in parseInt() function
e = parseInt(" 100 ");
console.log('parseInt(" 100 ") = ' +
    e);

// Base 16(hexadecimal)
f = parseInt("0x16");
console.log('parseInt("0x16") = ' +
    f);

Output

parseInt("100",10) = 100
parseInt("8",8) = NaN
parseInt("15",8) = 13
parseInt("16",16) = 22
parseInt(" 100 ") = 100
parseInt("0x16") = 22

Explanation:

The code demonstrates the parseInt() method with different radix values and string formats:

• "100" parsed in base 10 yields 100.
• "8" parsed in base 8 yields 8.
• "15" parsed in base 8 (treated as octal) yields 13.
• "16" parsed in base 16 (hexadecimal) yields 22.
• Leading and trailing spaces are ignored; " 100 " yields 100.
• "0x16" is treated as hexadecimal and yields 22.

We have a complete list of JavaScript Number constructor, properties, and methods list, to know more about the numbers please go through that article.

Supported Browsers

• Google Chrome
• Edge
• Internet Explorer 
• Firefox
• Opera
• Safari