CoreJS: Factory and Array Practice

Review: this pitfalls

There's a problem in the code below:

function talk() {
    console.log(this.noise);
}

var animals = [dog, cat, canary];
animals.allTalk = function() {
    this.forEach(talk);
}
animals.allTalk(); // failure!

Identify the problem and fix it! Rewrite the allTalk method of array animals to
make each animal talk. You must use function talk without changing its definition, and forEach(something). something should be a function which is not talk but instead somehow calls talk.

Embedding JS in HTML

Write an HTML file which embeds a javascript file in a <script> tag.

As you complete the exercises below, save them in that javascript file so that they can be run by loading your HTML file.

Finding one's marbles

1. Write a marble factory which can generate marbles with a custom size and color (having a property for each).

2. Give each marble instance a method isBigger(other) which returns true if it is bigger than another marble, other. Attach that method to the factory initially, then link each marble instance to it, so that they all share the same function.

In the bag

Next, you'll implement an abstract data structure for a bag, which contains multiple items (e.g. marbles) jumbled together.

1. Write a factory function makeBag(items) which makes bag instances. Each bag holds a collection of items, and the parameter items is an array listing the items the bag starts with (though more may be added). Each bag instance should have the following methods:

   1. put(item): places item into the bag in an unspecified position.
   2. draw(): removes a random item from the bag and returns it.
   3. divide(criterionFn): removes from the bag all items for which the callback criterionFn(item) returns truthy, and returns a new bag with just those items. The original bag will retain the items not matching criterionFn.
   4. serialize(compareFn): returns an array containing all items in the bag, sorted according to compareFn.

2. Make a bag and fill it with 100 marbles of random size 1-4, with (nearly) equal numbers of red, blue, and green.

   1. Use your divide method to extract the red marbles into another bag.
   2. serialize the red marbles into an array sorted by marble size, large to small.
   3. serialize the non-red marbles from the original bag, sorted by color (blues before greens).

3. Make another bag which holds the names of everyone in the class. Serialize it in reverse alphabetical order.

Samples

scratchpad

console