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How to add value to if (!this.value)

I am trying to enable my code in javascript to only allow numbers to be entered into a field. Therefore, I need the (!this.value) to equal [a-zA-Z]. How can I accomplish this?

function validatemycode()
$('datagroup').on('blur', 'input[id^="datagroup_1"]', function ()
if (!this.value)
alert('Alert message here.');

)



4 Answers
4

A Regex-free edition:

function validatemycode()
$('datagroup').on('blur', 'input[id^="datagroup_1"]', function ()
if (!isValidInput(this.value))
alert('Alert message here.');

);


function isValidInput(value)
var allowedCharacters = '0123456789'.split('');
return string.split('').every(function (char)
return allowedCharacters.includes(char);
);



What happens in isValidInput is:
1. We make an array out of 0123456789 (=['1','2','3','4','5','6','7','8','9']).

isValidInput

0123456789

['1','2','3','4','5','6','7','8','9']

We make an array out of the input (same as in the previous step).

every returns true if all of the elements of the array passes the test, which is: is the current character (of the original string) is included in the allowedCharacters array. If there's a character that is not a number, we return false.

every

true

allowedCharacters

false

This is also a nice exercise in functional programming.

Note: this won't work on Internet Explorer (since includes is not supported there).

includes

blur

keydown

keyup

preventDefault()

includes

You can use RegExp to check if there's any char that is not a number [^0-9]

RegExp

[^0-9]

$('.datagroup').on('blur', function () this.value.match(new RegExp("[^0-9]", "g")))
console.log('Not Ok');
else
console.log("Ok")

)

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input class="datagroup"/>

input

match()

RegExp

You can use a method to check whether or not the string contains something other than numbers. See below:

var containsLettersOrCharacters = function(value)

var split = value.split('');

for(var i = 0; i < split.length; i++)

if(isNaN(Number(split[i])))
return true;




return false;




Here we're breaking the string into individual characters using split(), then looping through each one and checking whether the value of Number(character) is NaN. If isNaN() returns true here, that means that the character isn't a number.

split()

Number(character)

NaN

isNaN()

The important thing here is that Number() against a string other than a number in string format will result in a NaN value.

Can use this as such:

if(containsLettersOrCharacters(value))
//the string contained something other than numbers



Hope this helps.

You could use RegExp.prototype.test() , that returns true or false.

var a = "abcABC";
var b = 1321321;
var c = "21321abc";
var d = "132 1321 ";


//only numbers
console.log(/^[0-9]+$/g.test(a))
console.log(/^[0-9]+$/g.test(b))
console.log(/^[0-9]+$/g.test(c))
console.log(/^[0-9]+$/g.test(d))

in your code:

function validatemycode()
$('datagroup').on('blur', 'input[id^="datagroup_1"]', function ()
if (/^[0-9]+$/g.test(this.value))
alert('Alert message here.');

)



[a-zA-Z]

*

%

/[0-9]/g.test(a)

abc123

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