如何检查我的范围变量是否实际包含NaN？

Question

How do i check if my scope variable actually contains NaN?

isNaN($scope.variable) returns true even if $scope.variable == undefined.

I want to set form validity true if scope variable actually contains NaN but not undefined .

Answer 1

Well the problem is that isNaN converts argument to Number type if it's not a number already, and since ToNumber(undefined) is indeed NaN you get this behavior.

So you can Number.isNaN() which was introduced in ES2015 to fix this confusion or add additional check whether the value is of Number type, so basically polyfilling this Number.isNaN :

$scope.variable == undefined.
// ...
typeof $scope.variable == 'number' && isNaN($scope.variable); // => false