Im sharing my visual thinking and notes from the first chapter of Eloquent JavaScript going through the short-circuiting of logical operators ||
and &&
. This can be useful when thinking about a value you want to return conditionally and logically
“Another important property of these two operators (||
and &&
) is that the part to their right is evaluated only when necessary. In the case of true || X
, no matter what X
 is—even if it’s a piece of program that does something terrible—the result will be true
, and X
 is never evaluated. The same goes for false && X
, which is false
and will ignore X
. This is called short-circuit evaluation.”
Two-bullet summary of this is:
- When using
||
, we are looking for a true left side to return it otherwise we return the right side - When using
&&
, we are looking for a false left to return it otherwise we return the right side.
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