Guide to Converting a String to a Number: JavaScript Programming

convert string to number javascript

Changing the type of a value in JavaScript is actually not that difficult. The programming language has built-in functions to allow you to convert types easily. In this post, we’ll look at how to convert a string to a number in JavaScript. We’ll also discuss the importance to convert string to number javascript and some practical usage scenarios. Finally, we’ll give you some tips to follow for optimum results.

Importance of Converting Strings to Numbers

There are several reasons why you might want to convert a string to a number in JavaScript.

The most common reason is that you need to perform mathematical operations on that value. For example, if you have a string like “5”, you can’t just add 1 to it and expect the result to be 6. You need first to convert it to a number, perform the calculation, and then convert it back to a string if necessary.

Another reason why you might need to convert a string is that you’re reading in values from an external source, like user input or from a file. The values will always be strings in these cases, so you’ll need to convert them before using them in your program.

How to Convert a String To A Number in JavaScript

JavaScript has two built-in methods for converting strings to numbers: parseInt() and parseFloat(). Both these methods are part of the global window object, so you don’t need to import any additional libraries to use them.

The main difference between these two methods is that parseInt() only returns whole numbers while parseFloat() can return fractional numbers as well.

Let’s take a look at an example:

parseInt(“5”); // Returns 5
parseFloat(“5”); // Also returns 5
parseInt(“5.5”); // Returns 5
parseFloat(“5.5”); // Returns 5.5

As you can see from the above code, both parseInt() and parseFloat() can be used to convert strings containing whole numbers with no decimal point. However, only parseFloat() can be used for strings containing fractional numbers. If you try to use parseInt() for these kinds of strings, it will simply stop parsing at the decimal point and return the whole number before it.

Practical usage scenario

Although JavaScript is a versatile language that can be used for a variety of purposes, one of its most common uses is web development. When working with data in JavaScript, it’s often necessary to convert strings to numbers.

For example, if a user inputs their age as a string, it would be useful to convert it to a number so that mathematical operations could be performed on it. Luckily, JavaScript provides a built-in function for converting strings to numbers: parseInt(). This function takes a string as an argument and returns the corresponding integer.


Converting strings into numbers is a common task that every JavaScript programmer deals with on a daily basis. Fortunately, JS provides built-in methods like parseInt() and parseFloat(), which make conversion relatively easy.

In this post, we looked at how these methods work and some practical usage scenarios for them. Finally, we gave some tips on what factors you should keep in mind when converting strings into numbers. Thanks for reading!