Javascript && operator versus nested if statements: what is faster?

Question

Now, before you all jump on me and say "you're over concerned about performance," let it hereby stand that I ask this more out of curiosity than rather an overzealous nature. That said...

I am curious if there is a performance difference between use of the && ("and") operator and nested if statements. Also, is there an actual processing difference? I.e., does && always process both statements, or will it stop @ the first one if the first one fails? How would that be different than nested if statements?

Examples to be clear:

A) && ("and") operator

if(a == b && c == d) { ...perform some code fashizzle... } 

versus B) nested if statements

if(a == b) {     if(c == d) { ...perform some code fashizzle... } } 

Answer 1

The performance difference is negligible. The && operator won't check the right hand expression when the left hand expression evaluates false. However, the & operator will check both regardless, maybe your confusion is caused by this fact.

In this particular example, I'd just choose the one using &&, since that's better readable.