How to Check if String is a Positive Integer in JavaScript

Sometimes you will come across strings that contain numbers, or are entirely made up of numbers.

When this happens, you might want to be able to check if the string is a positive integer so you can do some math with it.

In this post, we'll learn how to check if a string is a positive integer in JavaScript.

How to check if a string is a positive integer

To begin, let's start off with our example string:

	const string = "123";

To check if a string is a positive integer, we first must convert the string into a number.

We can do this by using the Number constructor.

	const string = "123";

const number = Number(string);

console.log(number);

	123

Now we must determine if this number is an integer.

We can do this by using the Number.isInteger() function, which accepts a string and returns a boolean value.

	const string = "123";

const number = Number(string);
const isInteger = Number.isInteger(number);

console.log(isInteger);

	true

Now that we've determined the number is an integer, we can just check that it is greater than 0 to confirm that it is a positive integer:

	const string = "123";

const number = Number(string);
const isInteger = Number.isInteger(number);
const isPositive = number > 0;
const isPositiveInteger = isInteger && isPositive;

console.log(isPositiveInteger);

	true

We can wrap this up into a reusable function:

	const isPositiveInteger = string => {
    const number = Number(string);
    const isInteger = Number.isInteger(number);
    const isPositive = number > 0;

    return isInteger && isPositive;
}

const results = isPositiveInteger("123");

console.log(results);

	true

Conclusion

In this post, we learned how to check if a string is an integer greater than 0.

Simply use the Number constructor to convert the string into a number, and then use the Number.isInteger() function to determine if the number is an integer, then check if the number is greater than 0.

Thanks for reading!

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