undefined, null, typeof

 

alert(typeof(count)); alert("isNaN:"+isNaN(count)); var isNullValue = (count == null); var isUndefinedValue = (count == undefined); var isNull = (count === null); var isUndefined = (count === null); alert("isNullValue :"+ isNullValue +" isNull :"+isNull ); alert("isUndefinedValue :"+ isUndefinedValue +" isUndefined : "+isUndefined); alert('count:' + count + ', isNullValue:'+ isNullValue + ', isUndefinedValue:'+isUndefinedValue + ', isNull:'+ isNull + ', isUndefined:'+isUndefined);