JavaScript Number parseInt() Method

JavaScript parseInt() Method is used to accept the string and radix parameter and convert it into an integer. The radix parameter is used to specify which numeral system to be used, for example, a radix of 16 (hexadecimal) indicates that the number in the string should be parsed from a hexadecimal number to a decimal number. If the string does not contain a numeric value then it returns NaN i.e, not a number. 

Note: This method is deprecated.

Syntax:

parseInt(Value, radix)

Parameters: This method accepts two parameters as mentioned above and described below:

• 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.

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

Below is an example of the parseInt() method:

Example 1:

javascript

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

Output:

Using parseInt("3.14") = 3

Example 2:

javascript

a = parseInt("100");
console.log('parseInt("100") = ' +
    a);

// It returns a Integer until
// it encounters Not a Number character
b = parseInt("2018@geeksforgeeks");
console.log('parseInt("2018@geeksforgeeks") = ' +
    b);

// It returns NaN on Non numeral character
c = parseInt("geeksforgeeks@2018");
console.log('parseInt("geeksforgeeks@2018") = ' +
    c);

// It returns Integer value of a Floating point Number
d = parseInt("3.14");
console.log('parseInt("3.14") = ' + d);

// It returns only first Number it encounters
e = parseInt("21 7 2018");
console.log('parseInt("21 7 2018") = ' +
    e);

Output: The n contains 2018 as ‘@’ is not a Number and parsing stop at that point, further characters are ignored.

parseInt("100") = 100
parseInt("2018@geeksforgeeks") = 2018
parseInt("geeksforgeeks@2018") = NaN
parseInt("3.14") = 3
parseInt("21 7 2018") = 21

Example 3: In this example, 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:  If the radix is not mentioned in the parseInt() function and the start of the string contains “0x” then it is treated as a hexadecimal value. By default, the radix is 10 (decimal).

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

Supported Browsers:

• Google Chrome 1 and above
• Edge 12 and above
• Firefox 1 and above
• Safari 1 and above
• Opera 3 and above

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