Regex to only allow numbers under 10 digits?

You can do this way:

/^[0-9]{1,10}$/

Code:

var tempVal = $('#targetMe').val();
if (/^[0-9]{1,10}$/.test(+tempVal)) // OR if (/^[0-9]{1,10}$/.test(+tempVal) && tempVal.length<=10) 
  alert('we cool');
else
  alert('we not');

Refer LIVE DEMO

var value = $('#targetMe').val(),
    re    = /^[1-9][0-9]{0,8}$/;

if (re.test(value)) {
    // ok
}

Would you need a regular expression?

var value = +$('#targetMe').val();
if (value && value<9999999999) { /*etc.*/ }