In this blog post, we learn how to check or validate a string containing only numbers. Often this validation is used to validate the phone number.
1. First Method using RegExp \D
To validate I am using RegExp \D Metacharacter. The \D metacharacter matches non-digit characters. “isNum” variable returns a true or false.
// a string
const str = "14755";
let isNum= /^\d+$/.test(str);
if(isNum){
console.log("A number.");
}else{
console.log("Not a number.");
}
Result
A number.
2. Second Method using parseInt()
The parseInt()
the function parses a string argument and returns an integer of the specified radix.
var value = "78544";
if(parseInt(value)) {
console.log(value+" is a number.");
}
else {
console.log(value+" is not a number.");
}
Result
78544 is a number.

Brijpal Sharma is a web developer with a passion for writing tech tutorials. Learn JavaScript and other web development technology.