multiple expressions in one switch statement

Question

It is my first time using the switch statement in Javascript. Is there a way to evaluate multiple conditions one switch statement, like so:

var i = 1;
switch(i && random(1)<0.3) {
    case (1):
        //code block
         break;
    case (2):
        //code block
} 

So that the code blocks would execute if both of the conditions were true?

Solution 1

You could do something like this:

var i = 1;
switch((i==1) + (Math.random(1)<0.3)*2) {
    case 0:
        //code block when neither is true
         break;
    case 1:
        //code block when only i == 1
         break;
    case 2:
        //code block when only random(1)<0.3
         break;
    case 3:
        //code block when both i==1 and random(1)<0.3
        break;
} 

... but it is not really the nicest code, and can easily lead to mistakes when one of the tested expressions is anything else than 0 or 1 (false or true).

It is better to use if ... else constructs to deal with this:

var i = 1;
var small = Math.random(1)<0.3;
if (i==1) {
    if (small) {
        //code block when both i==1 and random(1)<0.3
    } else {
        //code block when only i == 1
    }
} else if (small) {
    //code block when only random(1)<0.3
} else {
    //code block when neither is true
}

Solution 2

It's possible to write switch statements this way:

switch (true) {
  case a && b:
    // do smth
    break;
  case a && !b:
    // do other thing
    break;
}

The only thing you need to keep in mind is that && can return not only boolean, but rather any other value if e.g. 'a' (in code snippet above) resolves to some false value. If 'b' is string - then a && b, where a is false, shall return a string.
So when you use this pattern always ensure that the right side of && expression resolves to a boolean.