How to Convert a String to a Number in NodeJS

Introduction

How do you convert a string to a number in Node.js?

You can convert a string to a number in Node.js using any of these three methods:

`Number()`

, `parseInt()`

, or `parseFloat()`

.
In this article, we'll go over each method and how to use them in your code.

Let's get started!

Table of Contents

Method 1 — Number()

The first method we'll cover is the

`Number()`

constructor that takes a value as a parameter and attempts to convert it to a number. If the value passed to the `Number()`

constructor can't be converted to a number, `NaN`

is returned.
Here's an example of how you'd use it in your code:

Node.js

Number("25")

// returns 25 (typeof === number)

We pass a string value of

`"25"`

to the `Number()`

constructor and it returns a new number value of `25`

. If you checked the `typeof`

value for the new value, you'd find that it was transformed successfully from a string to a number.
Here are some more examples with different variations of strings passed as arguments:

Node.js

Number("25") // returns 25

Number("25.51") // returns 25.51

Number("25px") // returns NaN

Number("25.5something") // returns NaN

Pretty easy to work with, right?

Method 2 — parseInt()

The

`parseInt()`

is a function that parses a string and returns an integer with a specific radix. The function takes both a string and an optional radix integer value as parameters.
Here's a code example:

Node.js

parseInt("25")

// returns 25 (typeof === number)

We give the

`parseInt()`

function a `"25"`

string as a parameter and it returns a value of `25`

. And the new value is a number instead of a string.
Here are some additional examples with other variations of strings:

Node.js

parseInt("25") // returns 25

parseInt("25.51") // returns 25

parseInt("25px") // returns 25

parseInt("25.5something") // returns 25

Unlike the previous

`Number()`

method, notice that all of the four example strings were converted to a `25`

number value. In those cases, the `Number()`

method returned a value of `NaN`

instead.
Method 3 — parseFloat()

The last method we'll go over is the

`parseFloat()`

function that takes a string and converts it to a number with decimals (known as a point number).
Here's what it looks like in code:

Node.js

parseFloat("25")

// returns 25 (typeof === number)

Just like the previous two examples, the

`parseFloat()`

function takes a string of `"25"`

and converts it into a number value of `25`

.
And here are some additional examples using the same string variations as the other methods:

Node.js

parseFloat("25") // returns 25

parseFloat("25.51") // returns 25.51

parseFloat("25px") // returns 25

parseFloat("25.5something") // returns 25.5

Notice that the results are very similar to the

`parseInt()`

method, besides the fact that `parseFloat()`

conserves the decimal points on the string values it converts.
Conclusion

In this article, we went over three different ways to convert a string to a number using Node.js. These methods included the following:

`Number()`

`parseInt()`

`parseFloat()`

Thanks for reading and happy coding!

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