Extract a number from a string using JavaScript

In this article, we will learn how we can extract the numbers if exist in a given string.

Method to Extract Numbers from Given String:

• Using the JavaScript match() method with regEx
• Using the JavaScript reduce() method with the spread operator
• Using the JavaScript replace() method with regEx

Method 1: Using the JavaScript match method with regEx

The number from a string in javascript can be extracted into an array of numbers by using the match method. This function takes a regular expression as an argument and extracts the number from the string. The regular expression for extracting a number is (/(\d+)/). 

Example 1: This example uses the match() function to extract numbers from strings with regular expressions. 

Javascript

// Function to extract numbers
function myGeeks() {

    // Input string
    let str = "jhkj7682834";
    console.log(str)

    // Using match with regEx
    let matches = str.match(/(\d+)/);

    // Display output if number extracted
    if (matches) {
        console.log(matches[0]);
    }
}

// Function call
myGeeks();

Output

jhkj7682834
7682834

Example 2: This example uses the match() function to extract numbers from strings. 

Javascript

// Function to extract numbers
function myGeeks() {

    // Input string
    let str = "foo35bar5jhkj88";
    console.log(str)

    // Using match with regEx
    let matches = str.match(/\d+/g);

    // Display output if number extracted
    if (matches) {
        console.log(matches[0] +', '+ matches[1]+', ' + matches[2]);
    }
}

// Function call
myGeeks();

Output

foo35bar5jhkj88
35, 5, 88

Method 2: Using the JavaScript reduce() method with the spread operator

The Javascript arr.reduce() method in JavaScript is used to reduce the array to a single value and executes a provided function for each value of the array (from left to right) and the return value of the function is stored in an accumulator. 

Syntax: 

array.reduce( function(total, currentValue, currentIndex, arr), 
initialValue )

Example: This example spread operator to convert into an array and the reduce method to extract all the numbers from the string.

Javascript

// Function to extract numbers
function myGeeks() {
    // Input string
    let str = "jhkj7682834";
    let c = "0123456789";
    console.log(str);
    function check(x) {
        return c.includes(x) ? true : false;
    }
    let matches = [...str].reduce(
        (x, y) => (check(y) ? x + y : x),"");

    // Display output if number extracted
    if (matches) {
        console.log(matches);
    }
}

// Function call
myGeeks();

Output

jhkj7682834
7682834

Method 3: Using the JavaScript replace() method with regEx

The string.replace() is an inbuilt method in JavaScript that is used to replace a part of the given string with another string or a regular expression. The original string will remain unchanged.
Syntax:

str.replace(value1, value2)

Example: In this example, we will use the JavaScript replace() method with regEx to extract the numbers out of given string

Javascript

// Function to extract numbers
function myGeeks() {
    // Input string
    let str = "jhkj7682834";
    console.log(str);

    // Using match with regEx
    let matches = str.replace(/[^0-9]/g, "");

    // Display output if number extracted
    if (matches) {
        console.log(matches);
    }
}

// Function call
myGeeks();

Output

jhkj7682834
7682834

JavaScript is best known for web page development but it is also used in a variety of non-browser environments. You can learn JavaScript from the ground up by following this JavaScript Tutorial and JavaScript Examples.