check variable whether is number or string in javascript

Question

does anyone know how can I check variable whether is number or string in javascript

Answer 1

Use typeof to determine the type of an item.

alert(typeof "Hello World");
alert(typeof 123);

Answer 2

Try this,

<script type="text/javascript">
var reInteger = /^\d+$/;

function isInteger (s)
{    
    return reInteger.test(s)
}

if(isInteger("1a11"))
   document.write("Int");
else
  document.write("Not an integer");

</script>

Answer 3

You're looking for isNaN():

<script type="text/javascript">
  alert(isNaN(123));
  alert(isNaN(-1.23));
  alert(isNaN(5-2));
  alert(isNaN(0));
  alert(isNaN("Hello"));
  alert(isNaN("2005/12/12"));
</script>

See JavaScript isNaN() Function at W3schools.com.

Answer 4

Best way to do that it's use isNaN + type casting:

function isNumber (o) {
  return ! isNaN (o-0);
}

isNumber ('123'); // true  
isNumber (5); // true  
isNumber ('q345'); // false