I am taking a cool online course about functional programming in JavaScript. I was following along just fine until the instructor used the Array.prototype.reject() and it did not work for me at run time.

I would like to use reject instead of a for loop because it is less code. But, my browser, NodeJS and Express Code consoles tell me that reject is not a function.

I researched other articles that discuss promise.reject is not a function, but provide solutions that do not make sense to my scenario.

Here is the example code in the course:

var animals = [

    { name: 'Fluffykins',   species: 'rabbit' },

    { name: 'Caro',         species: 'dog' },

    { name: 'Hamilton',     species: 'dog' },

    { name: 'Harold',       species: 'fish' },

    { name: 'Ursula',       species: 'cat' },

    { name: 'Jimmy',        species: 'fish' }

];





var isDog = function(animal){

    return animal.species === 'dog';

}



var otherAnimals = animals.reject(isDog);

The work-around with a for-loop:

var notDogs = animals.filter(function(animal){

    return animal.species !== 'dog';

});

Its output is:

> notDogs

[ { name: 'Fluffykins', species: 'rabbit' },

  { name: 'Harold', species: 'fish' },

  { name: 'Ursula', species: 'cat' },

  { name: 'Jimmy', species: 'fish' } ]

Please help me use Array.prototype.reject().

EditL

I found Array.prototype.reject() at GitHub/Array.prototype.reject)