function valNum(inNum {
   var RegEx = /[0-9]{1,8}\.?[0-9]{0,2}/;
   var ValidNumber = inNum.match(RegEx);
   return ValidNumber;
}

Validating a decimal such as a measurement of time or currency (10.5 or 0.4). This function will return the correct number. If you feed in "10.5foo" the function will spit back 10.5. If you feed in "bar" the function will return nothing.

Validate Decimals with Javascript

validation

JavaScript