underscore.js _.isNaN[Object]

Returns true if object is NaN.
Note: this is not the same as the native isNaN function, which will also return true if the variable is undefined.

返回true如果对象是NaN, 原生函数isNaN.undefined类型也将返回true。这里将返回false

_.isNaN(NaN);
=> true
isNaN(undefined);
=> true
_.isNaN(undefined);
=> false

源码:

  _.isNaN = function(obj) {
    return obj !== obj;
  };