JS/php: If vs Switch

[moneyman18]

Well I am wondering which is better to use in php and JS. Is it better to use a bunch of If statments or a switch? Obviously there are reason to use a switch or else there probably wouldn't be one if there was no reason for it. Is one faster than the other or something? I searched Google but could not find a definate answer to this. Any information is appreciated!

[Jordan]

I don't know if there is a difference behind the scenes (there may be some, but it depends on the language and compiler/engine), but the reason for the creation of the switch statement is so you have less to type. It also looks prettier and is more organized in my opinion.

You basically just need to figure out when you think it is best to use a switch statement. If you know you are only going to be testing on one variable and you are going to have three or more tests on that variable then it's probably a good idea to use it. I also like it's version of OR ( || ) which you can see below.

switch(x)
{
        case 1:
        case 2:
        {
                // This code will execute when x
                // is 1 or 2.
                break;
        }
}

There are times when you have less typing with an if statement, though. Turning the if statement below into a switch would be a lot of typing, especially since you are working with more than one variable.

if(x == 1 && (y == 2 || y == 3) || (x == 2 || x == 3) && y == 1)

[Chris]

I did some speed tests a while back and got no difference in JS... so I don't think that's the reason. I'm pretty sure Triad hit it on the nose... it's just an organizational structure to try to make things easier to handle and it's much more effective for a single variable structure. (Also, depending on spacing, it could eventually be smaller in total coding size, I believe.)

[Renegade]

I've never used switches before - any chance you could post a few more functional examples so I can get the hang of them?

[Jordan]

Sure.

They're really handy when you are testing integers or characters.

I know you've made flash games before, and a really good use I've had for my own games is getting user input with them. The keypress_detector is an integer which represents the most recent key pressed that is stored in the queue.

switch(keypress_detector)
{

      // If the user is pressing enter.
      case RETURN_VALUE:

            // Code

            break;

      // If the user is pressing either shift button.
      case LSHIFT_VALUE:
      case RSHIFT_VALUE:

            // Code

            break;

      // If the user is pressing the up arrow.
      case UP_VALUE:

            // Code

            break;

      // If the user is pressing the down arrow.
      case DOWN_VALUE:

            // Code

            break;

      // If the user is trying to quit the game.
      case ESCAPE_VALUE:

            // Code

            break;

      // If the user is pausing or unpausing the game.
      case p_VALUE:

            // Code
}

[Renegade]

The syntax in actionscript is pretty similar to JS, so that's exactly why I was asking ;d that does look a lot more useful than billions of if statements, at leat in some cases.


Can you have more than one case, or varuiable per case? such as case 1 || 2 || 3 ? just saw that you included that. thanks ;d

[Jordan]

What I posted above is actually C++ since all the values are enums which represent integers. It could be written the exact same way in JS, though.

The switch statement is basically same in every language.

[Bennett 🚀]

If you were to use it for different skins, would you just use:


switch(pb_skinid)
{
case1:
break;
}


And so on?

[Jordan]

Yes, but you need a space after the "case" word.

[Bennett 🚀]

That's implied THat was just a quick check.

[Jordan]

Just making sure. ;P

[Bennett 🚀]

I do know some javascript

[Chris]

I will throw out that I've seen some interesting switch statements before:

switch(true){
case (pb_username == "tobias"):
// Blah
break;
case (pb_username != "tobias" && somefunc()):
// Blah
break;
}

That way you can actually incorporate it like it is an if statement.

[Jordan]

You can do all kinds of weird things like that in Javascript. I don't think most programming languages would allow that, though.

[Chris]

Nov 15, 2009 14:06:09 GMT -8 Jordan said:

You can do all kinds of weird things like that in Javascript. I don't think most programming languages would allow that, though.

I saw that trick originally in PHP. However, I'm not sure about other languages. I think I remember something about Java being very strict with Switch statements and only allowing certain types of variables to be used.