Extract a Number from a String using JavaScript (original) (raw)

Last Updated : 09 Jan, 2025

We will extract the numbers if they exist in a given string. We will have a string and we need to print the numbers that are present in the given string in the console.

Extract a number from a string using JavaScript

Below are the methods to extract a number from string using JavaScript:

Table of Content

Using JavaScript match method with regEx
Using JavaScript reduce() method with the spread operator
Using JavaScript replace() method with regEx
Using JavaScript for loop
Using Array.prototype.filter with split

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

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.

**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

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.

**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

This approach loops through each character in the string and checks if it's a number using isNaN(). If the character is a number, it appends it to numberStr.

**Example: This example use for loop to extract all numbers present in the string.

JavaScript `

function extractNumbers(str) { let numbers = ""; for (let i = 0; i < str.length; i++) { if (!isNaN(str[i])) { numbers += str[i]; } } console.log(numbers) }

// Input string let str = "jhkj7682834hhdg237"; console.log(str); extractNumbers(str);

Output

jhkj7682834hhdg237 7682834237

Using Array.prototype.filter with split

Using Array.prototype.filter with split, you can extract numbers from a string by splitting the string into an array of characters, filtering out non-numeric characters, and joining the remaining characters back into a string.

**Example:

JavaScript `

let str = "The price is 123 dollars"; let number = str.split('').filter(char => !isNaN(char) && char !== ' ').join(''); console.log(number); // "123"

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.