Introduction to parseInt() in JavaScript

parseInt() is a built-in JavaScript function that is used to convert a string to an integer. This function takes two arguments – the string to be converted and an optional radix (base) parameter.

Syntax

The syntax of the parseInt() function is as follows:

parseInt(string, radix)

• string: The string to be converted to an integer. This can contain digits, signs, and non-digit characters.
• radix: An optional parameter that represents the base in which the string is written. If it is not specified, the default value is 10. It can be any number between 2 and 36.

How it works

The parseInt() function scans the input string from left to right until it encounters a non-digit character. It then returns the integer value of all the digits that it has already encountered. The radix parameter is used to determine the base of the number system used in the string.

Examples

1. Converting a string to an integer with the default radix value:

let str = '123';
let num = parseInt(str);
console.log(num); // Output: 123

2. Converting a string to an integer with a specified radix value:

let str = '0xFF'; // hexadecimal representation of number 255
let num = parseInt(str, 16);
console.log(num); // Output: 255

3. Converting a string to an integer with non-numeric characters:

let str = '123ABC';
let num = parseInt(str);
console.log(num); // Output: 123

Return value

The parseInt() function returns an integer value that is equivalent to the input string. If the string cannot be converted to a number, it returns NaN (Not a Number).

Conclusion

In conclusion, parseInt() is a useful function in JavaScript that allows you to convert strings to integers. It's important to understand the radix parameter and how it affects the conversion process. Knowing the behavior of the parseInt() function is essential when working with user inputs, form fields, or any other data involving number conversion.