Check whether a value is a number in JavaScript or jQuery

Possible Duplicate:
Validate numbers in JavaScript - IsNumeric()

var miscCharge = $("#miscCharge").val();

I want to check misCharge is number or not. Is there any method or easy way in jQuery or JavaScript to do this?

HTMl is

<g:textField name="miscCharge"  id ="miscCharge" value="" size="9" max="100000000000" min="0" />