JavaScript isNaN() Function returning unexpected result

Smith

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2568 Points

74 Posts

I am using isNan() method to check if a string is a valid number as:

var str='';
if(isNaN(str)){
  console.log('Not a Number!');
}else{
  console.log('Number!');
}

But it show 'Number'.

Views: 9812
Total Answered: 2
Total Marked As Answer: 1
Posted On: 25-Sep-2017 04:50

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Answers

ethanm Member 24 Points 2 Posts	See isNaN() method behaviour as: `isNaN(123) //false isNaN(-1.23) //false isNaN(5-2) //false isNaN(0) //false isNaN('123') //false isNaN('Hello') //true isNaN('2017/12/12') //true isNaN('') //false isNaN(true) //false isNaN(undefined) //true isNaN('NaN') //true isNaN(NaN) //true isNaN(0 / 0) //true` Posted On: 25-Sep-2017 05:11
Brian Moderator 2232 Points 14 Posts	The purpose of 'isNaN' is not really to test if something is not a number, but you can use it to test if something is the number NaN (since NaN===NaN returns false in JavaScript you can't use equality). You should use 'typeof' instead, and then isNaN as: `if((typeof str) === 'number' && !isNaN(str))` Posted On: 26-Sep-2017 02:08