Check if string contains only digits

Question

I want to check if a string contains only digits. I used this:

var isANumber = isNaN(theValue) === false;

if (isANumber){
    ..
}

But realized that it also allows + and - . Basically, I want to make sure an input contains ONLY digits and no other characters. Since +100 and -5 are both numbers, isNaN() is not the right way to go. Perhaps a regexp is what I need? Any tips?

Answer 1

怎么样

let isnum = /^\d+$/.test(val);

Answer 2

string.match(/^[0-9]+$/) != null;

Answer 3

String.prototype.isNumber = function(){return /^\d+$/.test(this);}
console.log("123123".isNumber()); // outputs true
console.log("+12".isNumber()); // outputs false

Answer 4

如果您甚至想支持浮点值（点分隔值），那么您可以使用以下表达式：

var isNumber = /^\d+\.\d+$/.test(value);

Answer 5

Here's another interesting, readable way to check if a string contains only digits.

This method works by splitting the string into an array using the spread operator , and then uses the every() method to test whether all elements (characters) in the array are included in the string of digits '0123456789' :

 const digits_only = string => [...string].every(c => '0123456789'.includes(c)); console.log(digits_only('123')); // true console.log(digits_only('+123')); // false console.log(digits_only('-123')); // false console.log(digits_only('123.')); // false console.log(digits_only('.123')); // false console.log(digits_only('123.0')); // false console.log(digits_only('0.123')); // false console.log(digits_only('Hello, world!')); // false

Answer 6

This is what you want

function isANumber(str){
  return !/\D/.test(str);
}

Answer 7

function isNumeric(x) {
    return parseFloat(x).toString() === x.toString();
}

Though this will return false on strings with leading or trailing zeroes.

Answer 8

Here is a solution without using regular expressions:

function onlyDigits(s) {
  for (let i = s.length - 1; i >= 0; i--) {
    const d = s.charCodeAt(i);
    if (d < 48 || d > 57) return false
  }
  return true
}

where 48 and 57 are the char codes for "0" and "9", respectively.

Answer 9

好吧，您可以使用以下正则表达式：

^\d+$

Answer 10

如果您需要在同一验证中使用整数和浮点数

/^\\d+\\.\\d+$|^\\d+$/.test(val)

Answer 11

if you want to include float values also you can use the following code

theValue=$('#balanceinput').val();
var isnum1 = /^\d*\.?\d+$/.test(theValue);
var isnum2 =  /^\d*\.?\d+$/.test(theValue.split("").reverse().join(""));
alert(isnum1+' '+isnum2);

this will test for only digits and digits separated with '.' the first test will cover values such as 0.1 and 0 but also .1 , it will not allow 0. so the solution that I propose is to reverse theValue so .1 will be 1. then the same regular expression will not allow it .

example :

 theValue=3.4; //isnum1=true , isnum2=true 
theValue=.4; //isnum1=true , isnum2=false 
theValue=3.; //isnum1=flase , isnum2=true 

Answer 12

I want to check if a string contains only digits. I used this:

var isANumber = isNaN(theValue) === false;

if (isANumber){
    ..
}

But realized that it also allows + and - . Basically, I want to make sure an input contains ONLY digits and no other characters. Since +100 and -5 are both numbers, isNaN() is not the right way to go. Perhaps a regexp is what I need? Any tips?

Answer 13

If you use jQuery:

$.isNumeric('1234'); // true
$.isNumeric('1ab4'); // false

Answer 14

I want to check if a string contains only digits. I used this:

var isANumber = isNaN(theValue) === false;

if (isANumber){
    ..
}

But realized that it also allows + and - . Basically, I want to make sure an input contains ONLY digits and no other characters. Since +100 and -5 are both numbers, isNaN() is not the right way to go. Perhaps a regexp is what I need? Any tips?

Answer 15

Here's a Solution without using regex

const  isdigit=(value)=>{
    const val=Number(value)?true:false
    console.log(val);
    return val
}

isdigit("10")//true
isdigit("any String")//false

Answer 16

If you want to leave room for . you can try the below regex.

/[^0-9.]/g

Answer 17

c="123".match(/\D/) == null #true
c="a12".match(/\D/) == null #false

If a string contains only digits it will return null