Question

I’ve a legacy script. This is a part from it:

var e = e ? e : event;

So, nothing wrong here. But I use ternary mainly for toogling. Can it safely be rewritten like this

var e = e || event;

Is there any hidden reason for not using this one?

Answer 1

In your example e will be used if it is NOT a falsy value, such as false, 0, "", null, undefined. Otherwise event will be used. In your case this should be save.

But there is some danger in using more complex logical expressions instead of if-then-else (or ternary). Here is an example:

result = value > 10 && getA() || getB()

If the guard value > 10 evaluates to true AND getA() returns a falsy value, then getB() will be returned. This is different from the if-then-else behavior, which would return the falsy result of getA().