Are you having trouble understanding how to Extract a Number from a String in JavaScript? Don’t stress over it! This article will describe the root cause of the issue and offer some solutions. Let’s move forward!

The way to Extract a Number from a string in JavaScript?

Before learning how to extract a number from a JS string, we should look at some information below.

We can use the match method in Javascript to do it and store it in an array of integers. This function removes the number from the string using a regular expression as an input.

Just use the replace function and a regular expression to extract numbers from a string with JavaScript.

Let’s practice a few techniques to understand how to go about it.

Method 1: Utilize JavaScript’s match() method

In the script below, there is the string value, including the number (1444231), which the string value would store in the string_contain_number variable.

const string_contain_number = "JavaScript contains 1444231 libraries"

Then attaching the match() method to the variable, include \d+ as an argument to make it look as match(/\d+/).

To locate a digit in a string, use the d metacharacter. To find a consecutive sequence of digits, we add the + to \d.

\d+ is a metacharacter in regular expressions (RegEx) that means “match 1 or more digits”.

The syntax of match() method:

string.match(regExp)

Parameters: The parameter, in this case, is “regExp” (regular expression), which will compare with the given string.

string_contain_number.match(/\d+/)

After those two steps, we will encounter the output as below and quickly fix the questions on how to get a number out of a string in javascript.

console.log(string_contain_number.match(/\d+/))

Here is all the code:

const string_contain_number = "JavaScript contains 1444231 libraries"
string_contain_number.match(/\d+/)
console.log(string_contain_number.match(/\d+/))

Output:

"1444231"

A string is compared to a regular expression using the String match() method, which then gives the results. Since the first element of the array in our case is the matched number, we access the 0 property using bracket notation to obtain it.

Method 2: Utilize JavaScript replace() Method 

To extract a number from the original string in JavaScript, all non-digit characters must be replaced by invoking the replace() method on a string with a regex.To eliminate any non-digit characters, we pass a regular expression that matches all of them, allowing us to replace them with an empty string. 

The syntax of replace() Method:

replace(pattern, replacement)

Parameters:

pattern: A string or an object with a Symbol can be used. A regular expression is a common example of the replace method. Any value without the Symbol.replace method will be converted to a string.

replacement: It can be either a string or a function. If it is a string, it will replace the substring that pattern matches. A variety of special replacement patterns are supported; see the section Specifying a string as the replacement below for more information.

Take a look at the example below:

const example_str = 'JavaScript has evolved over the past 25 years';
const extract_num = example_str.replace(/\D/g, '');
console.log(extract_num);

Output:

25

Any non-digit characters in a string are matched by the D metacharacter of regex.

The g flag instructs the regex to match each instance of a character other than a digit in the string.

Unless the global flag is supplied, the input string’s first non-digit character would be detected and swapped.

const example_str = 'JavaScript has evolved over the past 25 years';
const extract_num = example_str.replace(/\D/, '');
console.log(extract_num);

Output:

avaScript has evolved over the past 25 years

Conclusion 

We trust you’ve made the right decision to Extract a Number from a String in JavaScript. Additionally, we hope that this clarifies the situation you ran into and, perhaps, offers a few more ways to prevent it. Please feel free to comment if you run into any significant issues with this bug, and we’ll get back as soon as we can! We appreciate your reading.

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