JavaScript parseInt()

const stringDate = "1996";

// parse the string to decimal
let intDate = parseInt(stringDate, 10);
console.log(intDate)

// Output: 1996

parseInt() Syntax

The syntax of the parseInt() function is:

parseInt(string, radix)

parseInt() Parameters

The parseInt() function takes in:

• string - The value to parse. If it is not a string, it is converted to one using ToString abstract operation.
• radix (optional) - An integer between 2 and 36 representing the base in the numeral system.

parseInt() Return Value

• Returns an integer parsed from the given string.
• Returns NaN when:
  • radix is less than 2 or greater than 36.
  • The first non-whitespace character can't be converted to a number.

Example: Using parseInt()

console.log(parseInt("875.99", 10)); // 875

console.log(parseInt("F", 16)); // 15
console.log(parseInt("0xF"));  // 15 -> JavaScript consider 0x... to be hexadecimal

console.log(parseInt("-17", 8)); // -15

// int is detected till a non-numeric character
console.log(parseInt("85,123", 10)); // 85
console.log(parseInt("FXX123", 16)); // 15

console.log(parseInt("45", 13)); // 57

console.log(parseInt("Hello", 8)); // NaN
console.log(parseInt("546", 2)); // NaN -> Invalud as binary has only 1 or 0

// BigInt values lose precision
console.log(parseInt("464546416543075614n")); // 464546416543075600

Output

875
15
15
-15
85
15
57
NaN
NaN
464546416543075600

Recommended Reading: Javascript parseFloat()