For example suppose I have
var myVar;
If I do
console.log((myVar != undefined) && true);
It returns false as expected. Is it possible to do something closer to
console.log(myVar && true);
It's much less verbose. At the moment the above returns undefined I would like false.
If I'm understanding you correctly, you want to turn undefined and false into false and true into true. If so, this should work fine:
console.log(!!myVar);
Each ! converts the value to a boolean and returns the opposite. The opposite of the opposite is the same as the original, except for that "converts to a boolean" part, which is exactly what you want.
For more information, see this question.
One way to drag a boolean out of a "truthy" or "falsy" value is to use !!
console.log(!!myVar);
