Check if value is a number

问题:

How can i simply check if a returned value of type int or uint is a number?

回答1:

Simple:

if(_myValue is Number)
{
    fire();

}// end if

[UPDATE]

Keep in mind that if _myValue is of type int or uint, then (_myValue is Number) will also equate to true. If you want to know if _myValue is a number that isn't an integer(int) or unsigned integer (uint), in other words a float, then you can simply modify the conditional as follows:

(_myValue is Number && !(_myValue is int) && !(_myValue is uint))

Let's look at an example:

package 
{
    import flash.display.Sprite;
    import flash.events.Event;

    public class Main extends Sprite 
    {

        public function Main():void 
        {
            if (stage) init();
            else addEventListener(Event.ADDED_TO_STAGE, init);
        }

        private function init(e:Event = null):void 
        {
            removeEventListener(Event.ADDED_TO_STAGE, init);

            var number1:Object = 1; // int
            var number2:Object = 1.1; // float
            var number3:Object = 0x000000; // uint

            trace(number1 is Number); // true
            trace(number2 is Number); // true
            trace(number3 is Number); // true

            trace(number1 is Number && !(number1 is int) && !(number1 is uint)); // false
            trace(number2 is Number && !(number2 is int) && !(number2 is uint)); // true
            trace(number3 is Number && !(number3 is int) && !(number3 is uint)); // false

        }

    }

}

回答2:

If you only want to know if myValue is one of the numeric types (Number, int, uint), you can check if (_myValue is Number) as Taurayi suggested.

If you also want to know if _myValue is a numeric string (like "6320" or "5.987"), use this:

if (!isNaN(Number(_myValue)))
{
    fire();
}

It uses Number(_myValue) to cast _myValue to the Number class. If Number is unable to convert it into a useful number it will return NaN, so we use !isNaN() to make sure the returned value is not "not a number".

It will return true for any variable of type Number (as long as its value isn't NaN), int, uint, and strings that contain a valid representation of a number.

回答3:

These methods could be problematic if you wish to check the input of a text field, which is 'always' a string. If you have a string with "123" and check with "123" is Number, you will get a false. So Number("123") would give true, but then again so will Number("lalala") (event though the result is NaN which will tell you NaN is Number (true).

To work with string you could do:

var s:String = "1234";
String(Number(s)) == String(s);
--True

var s:String = "lalala";
String(Number(s)) == String(s);
--False

回答4:

There are

• isNaN (You will want to negate this)
• typeof (Not sure how strongly type Number works)
• and is (which was already mentioned, again I am not sure how strong, types hold)