filter()

Example 1:
Filter out or sort some products.
Classic Use Case --> Only show me some specific type, i.e: vegetable

var products = [
  { name: 'cucumber', type: 'vegetable' },
  { name: 'banana', type: 'fruit' },
  { name: 'celery', type: 'vegetable' },
  { name: 'orange', type: 'fruit' }
];

products.filter(function(product) {
    return product.type === 'vegetable';
});

We create a new subset, don't want to modify the original array

Don't forget to include the return!

Another example with more conditions:
Type is vegetable, quantity is greater than 0, prices is less than 10

products.filter(function(product) {
  return product.type === 'vegetable'
      && product.quantity > 0
      && product.price < 15
});

Example 2: Give me the list of comments that belong to a particular post.

var post = { id: 4, title: 'New Post' };
var comments = [
  { postId: 4, content: 'awesome post' },
  { postId: 3, content: 'it was ok' },
  { postId: 4, content: 'neat' }
];

function commentsForPost(post, comments) {
    return comments.filter(function(comment) {
      return comment.postId === post.id;
  });
}

commentsForPost(post, comments);

Exercise: Filtering Values Filter the array of numbers using the filter helper, creating a new array that only contains numbers greater than 50.
Assign this new array to a variable called 'filteredNumbers'. Don't forget to use the 'return' keyword in the function!

var numbers = [15, 25, 35, 45, 55, 65, 75, 85, 95];
// number > 50
var filteredNumbers =[];

function filterOne(numbers) {
  return numbers.filter(function(number) {
        if (number > 50) {
              return filteredNumbers.push(number);
        }
    });
}

filterOne(numbers);

Exercise: Handling Permissions with Filter Filter the array of users, only returning users who have admin level access.
Assign the result to the variable 'filteredUsers'. Don't forget to use the 'return' keyword in the function!

var users = [
 { id: 1, admin: true },
 { id: 2, admin: false },
 { id: 3, admin: false },
 { id: 4, admin: false },
 { id: 5, admin: true },
];

var filteredUsers = [];

function filterUsers(users) {
    return users.filter(function(user) {
        if (user.admin === true) {
            return filteredUsers.push(user);
        }
    });
}

filterUsers(users);

Exercise: Challenging! Implementing 'reject'. This is a hard one! Create a function called 'reject'.
Reject should work in the opposite way of 'filter' - if a function returns 'true', the item should *not* be included in the new array. Hint: you can reuse filter.

// For example:
var numbers = [10, 20, 30];

var lessThanFifteen = reject(numbers, function(number){
  return number > 15;
});

lessThanFifteen // [ 10 ];

function reject(array, iteratorFunction) {

}