Regex validation for integers, with leading zeros | Learning Curve- Perfect Tutorial for the beginers

Below script will validate the numbers using regex

it will allow
0
1

it will not allow

00,0000,01, 02 etc.
Regex using javascript

<script language="javascript">

var text = '-1';
var thisRegex = new RegExp('^(0|[1-9][0-9]*)$');
if(!thisRegex.test(text)){
    alert('fail');
}
else
{
alert('success');
}
     
</script>

var text = '-1';

var thisRegex = new RegExp('^(0|[1-9][0-9]*)$');

if(!thisRegex.test(text)){

alert('fail');

}

else

{

alert('success');

}

</script>

Regex using PHP

<?php
$str="dfsafdsa";
if (!preg_match("/^(0|[1-9][0-9]*)$/", $str))
    {echo "invalid";
        //$this->form_validation->set_message('regex_check', 'Please enter proper value for no of projects');
        return FALSE;
    }
    else
    {echo "valid";
        return TRUE;
    }

?>

<?php

$str="dfsafdsa";

if (!preg_match("/^(0|[1-9][0-9]*)$/", $str))

{echo "invalid";

//$this->form_validation->set_message('regex_check', 'Please enter proper value for no of projects');

return FALSE;

}

else

{echo "valid";

return TRUE;

}