How To Check If String Contains Numbers In JavaScript

In JavaScript, you might need to check if a string contains numbers. This can be useful for various tasks, such as data validation, input filtering, or text processing. In this tutorial you will learn two ways for checking if a string contains numbers in JavaScript with code examples.

Using Regular Expressions in JavaScript

One of the most versatile and efficient ways to check if a string contains numbers is by using regular expressions. You can create a regular expression pattern that matches any digit (0-9) and then use the test() method to check if the pattern exists in the string. Here’s an example of how to do this:

function containsNumbers(inputString) {
    const regex = /\d/; // This regular expression matches any digit (0-9)
    return regex.test(inputString);
}

const testString = "Hello, 123 world!";

if (containsNumbers(testString)) {
    console.log("The string contains numbers.");
} else {
    console.log("The string does not contain numbers.");
}

In this example, the containsNumbers() function checks if the input string contains any digit. If it does, the function returns true, indicating that the string contains numbers.

Using for Loop to Check if String Contains Numbers

You can also use a loop to iterate through each character in the string and check if it is a digit. Because in JavaScript, strings are iterable, meaning you can iterate over them using loops or array iteration methods like forEach(), map(), filter(), etc. This is because strings are sequences of characters, and JavaScript treats them similarly to arrays of characters when it comes to iteration.

function containsNumbers(inputString) {
    for (let i = 0; i < inputString.length; i++) {
        if (!isNaN(parseInt(inputString[i]))) {
            return true;
        }
    }
    return false;
}

const testString = "Hello, 123 world!";

if (containsNumbers(testString)) {
    console.log("The string contains numbers.");
} else {
    console.log("The string does not contain numbers.");
}

In this example, the containsNumbers function iterates through each character in the input string and checks if it is a number using !isNaN(parseInt()) function. If it finds a number, it returns true.