# How to Convert a String to a Number in JavaScript

### Introduction to String to Number Conversion

In JavaScript, you often encounter scenarios where you need to convert a string to a number. This conversion is essential for performing mathematical operations or comparing values numerically. JavaScript provides several methods to convert strings to numbers, each with its own advantages and use cases. In this article, we will explore different techniques to convert a string to a number in JavaScript.

### Using the parseInt Function

One of the most commonly used methods to convert a string to an integer is the `parseInt` function. The `parseInt` function parses a string and returns an integer based on the provided radix. Here’s an example:

``````const str = "42";
const num = parseInt(str);

console.log(num);  // Output: 42
``````

In this example, we use the `parseInt` function to convert the string `"42"` to an integer. The resulting value is assigned to the `num` variable.

### Using the parseFloat Function

If you need to convert a string to a floating-point number, you can use the `parseFloat` function. The `parseFloat` function works similarly to `parseInt` but returns a floating-point number. Here’s an example:

``````const str = "3.14";
const num = parseFloat(str);

console.log(num);  // Output: 3.14
``````

In this example, we use the `parseFloat` function to convert the string `"3.14"` to a floating-point number. The resulting value is assigned to the `num` variable.

### Using the Number Constructor

JavaScript provides the `Number` constructor, which can be used to create a number object from a given value. When used as a function without the `new` keyword, the `Number` constructor converts the value to a primitive number. Here’s an example:

``````const str = "123";
const num = Number(str);

console.log(num);  // Output: 123
``````

In this example, we use the `Number` constructor to convert the string `"123"` to a number. The resulting value is assigned to the `num` variable.

### Using the Unary Plus Operator

An alternative approach to convert a string to a number is by using the unary plus operator (`+`). The unary plus operator converts its operand to a number. Here’s an example:

``````const str = "99";
const num = +str;

console.log(num);  // Output: 99
``````

In this example, we use the unary plus operator to convert the string `"99"` to a number. The resulting value is assigned to the `num` variable.

### Using the Global parseInt and parseFloat Functions

Apart from the `parseInt` and `parseFloat` functions, JavaScript also provides global functions with the same names. These global functions behave similarly to their respective methods, but they are not attached to the `Number` object. Here’s an example:

``````const str = "42";
const num = window.parseInt(str);

console.log(num);  // Output: 42
``````

In this example, we use the global `parseInt` function to convert the string `"42"` to an integer.

### Handling Invalid Strings

When converting a string to a number, it’s important to consider cases where the string cannot be parsed as a valid number. In such situations, the conversion will result in `NaN` (Not a Number). You can use the `isNaN` function to check if a value is `NaN`. Here’s an example:

``````const str = "hello";
const num = parseInt(str);

if (
``````
Mark Stain

My name is Mark Stein and I am an author of technical articles at EasyTechh. I do the parsing, writing and publishing of articles on various IT topics.