I don't understand how &&
, ||
, and !
work... both with bools and other data types. How do you use them?
All values in Javascript are either "truthy" or "falsy".
a && b
evaluates to the first falsy operanda || b
evaluates to the first truthy operandBoth operators will not evaluate any operands after the one the return.
If all operands don't match, it will evaluate to the last one.
!a
evaluates to true
if a
is falsy and false
if a
is truthy.All values are truthy except the following, which are falsy:
false
+0
-0
NaN
""
null
undefined
document.all
If you want to test that both of two conditions are truthy then use &&:
if (isX && isY)
{
// Do something.
}
If you want to test that one or both of two conditions are truthy then use ||:
if (isX || isY)
{
// Do something.
}
The !
inverts a boolean (a truthy value becomes false and vice versa).
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