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This argument can be used to specify the object that the function must be applied to. This will make accidental uses of properties that are not part of an object’s interface easier to spot.
Sure, duplicating the line is shorter than calling the Item. This object will use the direction names we saw earlier “n””ne”etcetera as property names. The properties of the prototype influence the object based on it, but the properties of this object never change the prototype.
That is not very practical. Jabascript.programowanie prevent this from happening too quickly, at leastwe add lichen to the terrarium. Every object is based on a prototype, which gives it a set of inherent properties.
It is part of the prototype of a rabbit. To keep things clear and organised, it is important to keep the amount of methods and responsibilities that an object type has as small as possible.
To make this easy, we can use a higher-order function that takes an action as its argument. The simple objects we have used so far are based on the most basic prototype, which is associated with the Object constructor. Make sure you have defined the randomElement function from exercise 8. Note that the action function is called with both the name of the property and the value it has in the object. In this new approach to prototypes, types that need no constructor can leave it out.
Unfortunately, none of them is quite perfect. Fortunately, this terrarium-simulator is not required to be accurate in any way, so we can get away with it.
If you need access to the whole this object, you can store that in a variable too. Right now it contains three cases which are typed in directly, or ‘hard-coded’:.
First, its constructor, which takes a plan an array of strings as argument, and initialises its grid. We use a ‘fake constructor’, and apply instanceof to it. Because you can use it to look things up by name, we will call it a Dictionary. Getting a list of the property names in a dictionary sounds like a useful tool to have, so we add it to the Dictionary prototype.
We could also use the each method in directions to build the array, which is better already. It would be nicer if it would print automatically.
Can you design a function methodwhich allows you to bind an object to one of its methods without naming the object twice? A trick similar to the clone function can be used to get around it: It would also look better if, instead of printing a thousand terraria below each other, we could update a single printout of the terrarium. Multiple inheritance, though extremely useful in some situations, can be safely ignored most of the time.
Adding some functions to take care of common operations can make things a little smoother. This can be solved by doing something even uglier: Of course, if you are careful, and you do not expect your code to have to coexist with badly-written code, adding methods to standard prototypes is a perfectly good technique. If we make the old prototype object the prototype of the new prototype object you may have to re-read that a few timesit will automatically have all its properties. The x coordinate of the positions on the grid can be used to determine when the end of a line is reached.
You give it the object on the left hand side, and a constructor on the right hand side, and it returns a boolean, true if the constructor’s prototype property is the direct or indirect prototype of the object, and false otherwise.
Modify the lichenPlan array to include a few of these, and try them out. You could try to make the lichen-eater-eaters ‘hibernate’ use the “wait” action for a whilewhen they fail to find food for a few turns.