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So-- the way to get the keys of an object, is this function called
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object.keys
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[TYPING]
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So, so by doing object.keys and passing in the object,
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we now have an array full of the string values of the keys in that object.
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And so what we're going to do is, we're going to iterate through those keys.
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Check to see if the value is of an object.
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If so, we'll go ahead and clone that.
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Let's not worry about functions, or any of those other things for now.
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Otherwise, just return that value.
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So, let's have this for loop--
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[TYPING]
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And do that.
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So first, let's define--
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[TYPING]
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The new objects that we're going to return.
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And let's just start with an empty object for now.
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And so, now we have to check to see if each of these values is an object.
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If so, copy it, otherwise return.
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So how are we going to check the type of a particular key?
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AUDIENCE: Type of operator.
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JORDAN: Yeah, exactly, that type of operator.
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So we can do if the type of obj, and then pass in by keys.
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[TYPING]
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So what do we want to check against?
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[TYPING]
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All right, what am I doing wrong here?
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AUDIENCE: Three equals.
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JORDAN: Yeah, we should always use that three equal signs.
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In this case it would matter.
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But, we should just get in the habit of doing that.
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I mean so if you notice here, we actually have bracket notation
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within bracket notation.
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That is totally fine.
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Cool.
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So, if something is an object to what are we going to turn?
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We can do object, new object with that key.
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[TYPING]
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Equals-- what?
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AUDIENCE: The value?
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Oh no, I'm sorry, deep copy.
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JORDAN: Yeah, let's actually deep copy that value to two.
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Otherwise--
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[TYPING]
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We can just set it equal to the other key.
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[TYPING]
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And then at the very end, we can just return that new object.
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[TYPING]
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Cool.
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Anybody see any bugs?
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Candy opportunity.
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All right, let's just go ahead and test this.
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So-- let's do--
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Do copy o--
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Then update o--
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[TYPING]
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o.obj.key Let's say of to new key.
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[TYPING]
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o3.obj.key.
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Get rid of that.
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All right, so moment of truth--
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[TYPING]
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Key, rather than new key.
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So we did it.
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Whew.
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All right, any other questions about--
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objects, mutating, references, any of that stuff?
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No, great.
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So, arrays as well, are also stored by reference.
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So if we were to do the same exact example,
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and rather than updating the object, we updated that array,
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we'd end up with the same exact results.
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And so, if we were to update our deep copy function to also take
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care of arrays, all we have to do is also check, rather than
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checking object, also check against arrays or any other data types
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that we're going to check.
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Let's move on to prototype inheritance.
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So what exactly is prototype inheritance?
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Well, so non-primitive types have a few properties and methods
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associated with them.
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So, array, we have this thing called array.push,
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which will add values to an array.
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So, say we have something like--
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[TYPING]
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An empty array, if we did array.push--
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some value, then array now has something in it.
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If we were to push another value into it--
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It now has two values in it.
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So array.prototype.push is a method that we
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have available on all arrays, that just adds new values to an array.
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Another one would be like, string.prototype.toUpperCase.
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So, say we were to have some string, so--
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[TYPING]
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If you do str.toUpperCase--
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Now we, we're left with a new string with all uppercase.
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So, these are just functions that we can invoke on any non-primitive that
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gives us something else.
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That is available to all non-primitives of a given type.
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So each object stores a reference to its prototype.
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