javascript - Determine if string is Date or Number -

i'm trying determine if string number or date.

here code:

this._getfieldformat = (value) => {    // check if date   let d = new date(value);    if (!isnan( d.gettime() ) ) {     return 'date';   }    // check if boolean   // isnan(false) = false, false number (0), true number (1)   if(typeof value  === 'boolean'){     return 'boolean';   }    // check if string number   if(!isnan(value)){     return 'number';   }    return typeof value; }; 

it works date like: 2016-04-19t23:09:10.208092z. problem 1 valid date (wed dec 31 1969 16:00:00 gmt-0800 (pst)) , isnan(new date()) return false (a date number).

any idea on how out of loop?

so happening called coercion. since javascript dynamic typing when give 2 different types js engine tries coerce 1 of types reasonable or thought meant.

for instance:

isnan("37"); false because "37" converted number 37 

isnan(new date()) return false (a date number)

it converted date number correct.

however, invalid values in date strings not recognized iso format defined ecma-262 may or may not result in nan, depending on browser , values provided

so

new date('23/25/2014'); // non-iso string invalid date values 

so return nan in browsers comply es5 , later.

also stricter check can use:

number.isnan(new date()); // should return true 

so recap make sure date conform iso standard or nan , use stricter check. hope helps.