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Welcome back.

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Let's talk about.

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Knowledge coalescing operator, and it's this double questionmark.

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So remember, we learned about the big event and we also learned about the optional training with the

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questionmark and the period just like this.

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So what's this double questionmark and this double questionmark can often be used instead of what we've

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seen before, the or operator.

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So let me show you what I mean.

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Let's imagine that we have a new property here and we'll call it power.

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And power for Pikachu is.

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Now, if I wanted to get the power of my Pokémon, then I can simply do this and grab the power or the

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property power lining.

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But let's say we weren't sure that we had this property for the Pokémon, so we can't really do questionmark

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period because, well, that doesn't really make sense.

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Remember, the optional chaining operator works on objects and checking their properties, but power

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is the end of the chain.

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We can't really do anything.

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So most of the time what we would do is do an hour operator.

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So if let's say Pikachu doesn't have a power, we can just say no power.

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So let's imagine here that we have an empty string or maybe not even the property, and if I copy this

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over and run this.

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I get no power that makes sense, right?

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But what if we had power in here?

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But it's an empty string.

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What would happen then?

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Well, if I run this again.

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I get no power again.

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And that is because this or operator works by checking if this is Truthy, if it's not Truthy, then

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it resorts to no power.

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That's how JavaScript works.

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So this empty string evaluates as false and I get no power.

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What if the power was false?

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Once again, this will resort to force and you'll get no power, but what if we wanted this to be an

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empty string instead of no power?

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We want to check if this is no or undefined.

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Only then do we want to give no power.

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Otherwise, maybe this Pikachu just is still evolving and doesn't have any power.

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But we don't necessarily want to say no power.

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Well, in that case, we can do the knowledge coalescing.

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And this instead of the OR operator doesn't check if a value is falsey.

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Instead, it checks if it's null or undefined.

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So things like zero, for example.

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If we do that, well, let's find out.

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If I copy this, I get power of zero.

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If this was an or.

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In that case, the result would be different.

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The result would be no power, even though we actually have a value.

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So, again, knowledge coalescing is really, really useful for those occasions that you might use the

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or operator.

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Pretty, pretty cool.

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All right.

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I think that's enough.

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There's a few more to cover with 20.

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But again, we're going to encounter those throughout the rest of the sections because they require

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a bit of other knowledge that we're going to accumulate.

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So let's take a break and I'll see you in the next one.