# How to use the parseInt() Function in JavaScript

`parseInt()` is a native JavaScript function that is used to convert strings into integers. In this tutorial, we will learn how to use it with int, float and hexadecimal strings.

## The parseInt() Syntax

The `parseInt()` function accepts the string to convert and an optional radix.

``````parseInt(string[, radix])
``````

• `string` – the string to convert.
• `radix` (optional) – the numerical system of the string.

## Convert Int String to Number

In the example below, we will convert a string containing an int into the data type of number.

``````var output = parseInt('222');

console.log(output);
console.log(typeof(output));
``````
``````222
number
``````

## Convert Decimal String to Number

When a decimal string is supplied to `parseInt()` everything after the decimal will be removed.

``````var output = parseInt('222.222');

console.log(output);
console.log(typeof(output));
``````
``````222
number
``````

## Convert Hexadecimal Number in a String to Number

A hex number is a base 16 number, to convert it into an integer with the data type of number in JavaScript supply the radix as the second argument like this:

``````var output = parseInt("0xF", 16);

console.log(output);
console.log(typeof(output));
``````
``````15
number
``````

## Things to Watch Out for with parseInt()

Here are some behaviours of `parseInt()` to watch out for:

``````parseInt('222kk222'); // everything after first non number is cut
``````
``````222
``````
``````parseInt('s123'); // strings starting with non-numerical value will return NaN
``````
``````NaN
``````

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