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
- Check if string is a number using isNaN() and Number()
- Check if string is a number using isNaN() and parseFloat()
- Check if string is a number using isNaN() and parseInt()
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.
Example 1:-
Check if the string “-567845” is a number
Code:-
Frequently Asked:
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let dummyString = '-567845' console.log( /^-?\d+$/.test(dummyString) )
Output:-
true
Example 2:-
Check if the string “567845.00” is a number
Code:-
let dummyString = '567845.00' console.log( /^-?\d+$/.test(dummyString) )
Output:-
false
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) { return !(Number.isNaN(Number(_string))) }
Example 1:-
Check if the string “-567845” is a number
let dummyString = '-567845' console.log(ifStringIsNumber(dummyString))
Output:-
true
Example 2:-
Check if the string “567845.00” is a number
let dummyString = '567845.00' console.log(ifStringIsNumber(dummyString))
Output:-
true
Example 3:-
Check if the string “0xa” is a number
let dummyString = '0xa' console.log(ifStringIsNumber(dummyString))
Output:-
true
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) { return !(Number.isNaN(parseFloat(_string))) }
Example 1:-
Check if the string “-567845” is a number
let dummyString = '-567845' console.log(ifStringIsNumber(dummyString))
Output:-
true
Example 2:-
Check if the string “567845.00” is a number
let dummyString = '567845.00' console.log(ifStringIsNumber(dummyString))
Output:-
true
Example 3:-
Check if the string “0xa“ is a number
let dummyString = '0xa' console.log(ifStringIsNumber(dummyString))
Output:-
true
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) { return !(Number.isNaN(parseInt(_string))) }
Example 1:-
Check if the string “-567845” is a number
let dummyString = '-567845' console.log(ifStringIsNumber(dummyString))
Output:-
true
Example 2:-
Check if the string “567845.00” is a number
let dummyString = '567845.00' console.log(ifStringIsNumber(dummyString))
Output:-
true
Example 3:-
Check if the string “0xa“ is a number
let dummyString = '0xa' console.log(ifStringIsNumber(dummyString))
Output:-
true
Read More:
- Javascript: Remove all but numbers from string
- Javascript: Check if a string contains numbers
- Javascript: Check if string contains substring
I hope this article helped you to check if the string is a number in javascript. Good Luck !!!