If You Don’t Understand Short Circuiting Your App Will Break

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[SirSidi]

Do not use short circuit just to ensure that a property exists. instead use optional chaining for that. It looks like this 'person?.name'

[zacharystudio]

great explanation, thanks! another way i think of this is, the `&&` operator is _searching for truthiness_, so when it evaluates the first `false`, it immediately knows the whole expression is _not true_, thus terminating at that point and not reading the additional conditions. whereas with the first `true`, _that condition_ is true, but `&&` states that _both_ must be true for the entire expression to evaluate as true, thus it continues on to check the next condition.

[mateoc]

Performance tip: In a case/switch statement put the most likely options first, avoiding comparison to less likely values unless necessary.

[ReadieFur]

When I discovered this ages ago it became so useful to me, I used it within of statements but didn’t know you could do it like this

[Jean-ykeo]

I used the && a lot in React when I want to render a component conditionally.

[JeremiahPayne]

Short circuiting is also useful if you have 2 things to evaluate but one of those things takes more compute than the other. Do the light one first then it only does the expensive one as needed

[YamiSuzume]

I would mention the difference between "&&" and "&" in this case, since later would also evaluate, even if the axiom does apply.

[SmithRyanHE]

Great video Kyle - Short, specific and to the point. You should probably mention that while demonstrated with JS, the concept is quite universal - nearly all modern languages, including SQL, employs this shortcut (though some let you disable it with compiler switches). For object presence testing It's especially useful in languages where optional chaining is not a thing.

[aviv]

You can use & one time instead && to check both sides.

[hadawardgz]

Short circuiting is no longer necessary these days, in the LTS 14 version of NodeJS they released optional chaining, which is much better:

person?.name

And if you want a default value you can use the null coalescence operator

person?.name ?? "Unknown"

[Rudxain]

This is also called lazy evaluation. An example of unexpected greedy evaluation is expressions within array literals:

let x = 0
[++x, x][1]
//returns 1 regardless if the index is 0 or 1.

This is because array literals evaluate and execute all expressions and functions within them, in the same order that the comma (", ") operator defines.

So be careful when you use array literals as a replacement for switch-case

[thegreatbambino]

The other important part is looking at what the return value is in each case. For both operators the return value may not be a boolean, it's the return value of the second statement in the event of a non short circuit

[brazzmo]

Note: Logical XOR (not bitwise XOR), can NEVER short circuit as both values need to be evaluated. C and C++ don't have a logical XOR operator built in due to this, as they've specified that a logical operator must be able to short circuit to exist, and should just be a function otherwise.

[feynthefallen]

That is actually the default behaviour in most cases. The really interesting cases are the ones where it suddenly doesn't apply any more, e.g. in BASH scripts: command1 && command2 || command3 is _not_ a short-circuit, no matter how much it looks like one.

[NoProblem]

Still rember the good old days when the order of boolean operation is undefined, depending on thr compiler, it could be LTR or RTL

[santiagomoebio]

It's also useful to run verifications in order of likelihood, putting the "deal breakers" first, and/or (pun intended) put the most expensive verifications later (so they are less likely to actually being calculated).

[PhillStone]

I didn't understand much of that (not a language I know yet) but I really like the presentation and editing. Look forward to the next video like this.

[Azserd]

that’s why order in if-else conditions is important

[busyrand]

This concept is all over React Development... It's great to know. I remember seeing and understanding it logically, but I didn't understand why it was used so much. Great video!

[abdulhakim]

Thank you, it make me understand why the second statement after ampersand doesn't run, when 1st statement is false.