Javascript check if string or number

How to check if string is number in JavaScript? [SOLVED]

Within our applications knowing the actual data type of the data we have is important, and being able to manipulate them properly is essential. One area we need it in is with numbers and strings. In JavaScript, there are various ways to check if a string is a number.

In this article, we will discuss three ways to check if a string is a number.

Method-1: Use the isNaN method to check if a string is a number

The most common way to check if a string is a number is to use the typeof operator. This operator returns the type of a variable, which is either string , number , boolean , undefined , or object . If the typeof operator returns number , then the variable is definitely a number. However, if the typeof operator returns string , then the string may or may not be a number. In order to check if a string is definitely not a number, you can use the isNaN() function. This function returns true if the value is not a number, and false if the value is a number.

let str = " 20"; let strJava = "javascript 20"; function isNumber(value) < if (typeof value === "string") < return !isNaN(value); >> console.log(isNumber(str)); console.log(isNumber(strJava)); 

As we can see it returns false when the string contained the number 20 regardless of the whitespace.

Method-2: Use the + operator to check if a string is a number

We can make use of the unary operator — + — which helps convert a string to a number. Using the same example as in the previous section, we can check if the string is a number.

let str = " 20"; let strJava = "javascript 20"; function isNumber(value) < const conv = +value; if (conv) < return true; >else < return false; >> console.log(isNumber(str)); console.log(isNumber(strJava)); 

Method-3: Use regex to check if a string is a number

Regular expression provides a way to check for number patterns within strings using the /\\d/ pattern and the test method which checks if the pattern exists within the string. A little modification to the regex pattern allows us to check if a string is a number.

let str = "20.2"; let strJava = "javascript 20"; function isNumber(value) < return /^-?\\d/.test(value); >console.log(isNumber(str)); console.log(isNumber(strJava)); 

Summary

We have provided three approaches to check if a string is a number; the isNaN method, the unary + operator, and regex . All of these approaches can be tweaked and improved depending on use cases.

References

Didn’t find what you were looking for? Perform a quick search across GoLinuxCloud

If my articles on GoLinuxCloud has helped you, kindly consider buying me a coffee as a token of appreciation.

For any other feedbacks or questions you can either use the comments section or contact me form.

Thank You for your support!!

1 thought on “How to check if string is number in JavaScript? [SOLVED]”

Leave a Comment Cancel reply

JavaScript Tutorial

• Beginner Guide
  • Define Global Variable
  • Working with Object Literals
  • Working with Template Literals
  • Classes Overview
  • Subclass Examples
  • Iterators and Generators
  • Error Handling
  • Date Formatting
  • parseFloat()
  • Array.pop()
  • Array.slice()
  • Array.unshift()
  • Array.join()
  • Array.findIndex()
  • Array Slicing Methods
  • Remove Element from Array
  • Check Array is Empty
  • Create Unique Array of Objects
  • Convert Array to String
  • String.toLowerCase()
  • String.toString()
  • String.trimEnd()
  • String.trim()
  • String.replaceAll()
  • String.startsWith()
  • replaceWith()
  • String.indexOf()
  • replaceAll() with regex
  • Check if String is Number
  • Check string contains spaces
  • Convert String to Boolean
  • Check String contains Substring
  • Compare Strings
  • Math.acos()
  • Math.abs()
  • Math.asin()
  • Math.atan()
  • Math.cbrt()
  • Math.ceil()
  • Math.cos()
  • Math.floor()
  • Math.fround()
  • Math.hypot()
  • Math.log()
  • Math max()
  • Math.power()
  • Math.random()
  • Math.toRadians()
  • Nested Function
  • Arrow Function
  • Optional Parameters
  • The arguments Object
  • Calling Vs Invoking a Function
  • Call a function every second
  • Using function as Values
  • Chaining Functions
  • if statement
  • Handling Special Characters
  • hide() Method
  • Set.add()
  • Remove Element from Set
  • DOM Selector Methods
  • Find Elements in DOM
  • Remove DOM Element
  • Replace DOM Element
  • Get DOM Element Width
  • addEventListener()
  • querySelector()
  • getBoundingClientRect()
  • NodeList
  • Node.insertBefore()
  • Event Bubbling
  • Parse JSON File
  • Parse YAML File
  • Parse CSV File
  • async function
  • await
  • Exponentiation (**)
  • Bitwise XOR (^)
  • Nullish Coalescing Operator (??)
  • Double Exclamation Mark (!!)
  • Spread Operator (. )
  • Destructuring assignment
  • instanceof Operator
  • Access map with index
  • Check map size
  • Sort map by value
  • Sort by date
  • Add days to date
  • date/time field value out of range
  • Promise Thenable Object
  • Promise.all()
  • Promise.resolve()
  • Promise.race()
  • Promise.reject()
  • Chaining Promises
  • Keyboard Events
  • Mouse Events
  • Singleton Pattern
  • Mediator Pattern
  • Observer Pattern
  • Factory Pattern

  Источник

  Check if string is a number in javascript

  While working in any language, a general requirement is encountered to check if a string is a number. Most user inputs are taken in the form of strings and processed further after checking various attributes. In this article, let’s check if the given string is a number.

  Table of Contents:-

  Check if string is a number using RegEx

  The simplest way to check if the string is a number or not is to use regular expressions, but one can use them to check if the string is a whole number.

  Suppose the requirement is a little more complex. In that case, we should not use regular expressions, for example, to check for hexadecimal, octal, or exponential, or decimal values.

  Frequently Asked:

  Check if the string “-567845” is a number

  let dummyString = '-567845' console.log( /^-?\d+$/.test(dummyString) )

  Check if the string “567845.00” is a number

  let dummyString = '567845.00' console.log( /^-?\d+$/.test(dummyString) )

  Check if string is a number using isNaN() and Number()

  The Number.isNaN() method of javascript determines if the passed value is Not-A-Number .

  The Number() function of javascript coverts a string or other value to the number type.

  Function Code:-

  function ifStringIsNumber(_string)

  Check if the string “-567845” is a number

  let dummyString = '-567845' console.log(ifStringIsNumber(dummyString))

  Check if the string “567845.00” is a number

  let dummyString = '567845.00' console.log(ifStringIsNumber(dummyString))

  Check if the string “0xa” is a number

  let dummyString = '0xa' console.log(ifStringIsNumber(dummyString))

  Note that the input ‘-0xa’ will return false.

  Check if string is a number using isNaN() and parseFloat()

  The parseFloat() method of javascript parses an argument and returns a floating-point number.

  Function Code:-

  function ifStringIsNumber(_string)

  Check if the string “-567845” is a number

  let dummyString = '-567845' console.log(ifStringIsNumber(dummyString))

  Check if the string “567845.00” is a number

  let dummyString = '567845.00' console.log(ifStringIsNumber(dummyString))

  Check if the string “ 0xa “ is a number

  let dummyString = '0xa' console.log(ifStringIsNumber(dummyString))

  Check if string is a number using isNaN() and parseInt()

  The parseInt() method of javascript parses an argument and returns an integer value.

  Function Code:-

  function ifStringIsNumber(_string)

  Check if the string “-567845” is a number

  let dummyString = '-567845' console.log(ifStringIsNumber(dummyString))

  Check if the string “567845.00” is a number

  let dummyString = '567845.00' console.log(ifStringIsNumber(dummyString))

  Check if the string “ 0xa “ is a number

  let dummyString = '0xa' console.log(ifStringIsNumber(dummyString))

  I hope this article helped you to check if the string is a number in javascript. Good Luck .

  Related posts:

  Share your love

  Leave a Comment Cancel Reply

  This site uses Akismet to reduce spam. Learn how your comment data is processed.

  Terms of Use

  Disclaimer

  Copyright © 2023 thisPointer

  To provide the best experiences, we and our partners use technologies like cookies to store and/or access device information. Consenting to these technologies will allow us and our partners to process personal data such as browsing behavior or unique IDs on this site and show (non-) personalized ads. Not consenting or withdrawing consent, may adversely affect certain features and functions.

  Click below to consent to the above or make granular choices. Your choices will be applied to this site only. You can change your settings at any time, including withdrawing your consent, by using the toggles on the Cookie Policy, or by clicking on the manage consent button at the bottom of the screen.

  The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network.

  The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user.

  The technical storage or access that is used exclusively for statistical purposes. The technical storage or access that is used exclusively for anonymous statistical purposes. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you.

  The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes.

  Источник