I found this line of code in a project and I couldn't under
return d.isPointInside(a, b) ? (console.log("runned"), c = !0, !1) : void 0
And I couldn't understand the part:
(console.log("runned"), c = !0, !1)
The word "runned" should be displayed in the browser's console, But need some help to understand the rest.
Just some type juggeling
!0 === true
!1 === false
void 0 === undefined
The result with some longer words:
(console.log("runned"), c = true, false);
The complete return statement reads as following, without use of the Comma Operator:
if (d.isPointInside(a, b)) {
console.log("runned");
c = true;
return false;
} else {
return undefined;
}
The commas just create a sequence, so ultimately this statement will return !1 which is false. The code is exploiting the sequence syntax to produce a byproduct of outputting to console and setting a variable.
It's similar to:
var a,b,c;
Which declares variables but doesn't do anything with them. This is equally valid:
var a=7,b=someComplexCalculation(),c;
!1 is false, and is kind of useless, but in JavaScript this is a useful form because it forces type to be Boolean. When developing, it may be useful to change !1 to !a, which is guaranteed to return a Boolean value.
The last value of the sequence completes the statement, and acts as the return value.
So:
X=(3, Math.sqrt(2), "something");
Will set X="something"
this statement will return !1 which is false you should expand on your answer.First, the code is using the comma operator in JavaScript that evaluate everything but only return the last element. For example var a = 1, 2, 3; will always be equal to 3 because only the last item gets returned.
With this in mind, let's look at the piece of code you didn't understand:
(console.log("runned"), c = !0, !1)
Due to the comma operator, this breaks up into three expressions that will be evaluated in a sequence:
console.log("runned")
Will print the given word in the console.
c = !0
Will assign the value of true to the variable c. This is because zero is a falsey value which when converted to the opposite using the not operator ! produces true.
`!1`
Finally the result of this expression will be returned from the entire section inside the brackets. Similar to the above, this uses the fact that 1 is a truthy value, so !1 will yield false.
So, taken as a whole, the code will print, assign a value, and return a value all in one line.
Given the syntax and the variables used, my assumption is that this is minified code. Minification uses the language rules in a similar manner in order to reduce the amount of characters used. In partucular !0 and !1 are very common replacements of true and false because they latter are at least half the length.
