Switch statement explained for beginners

[u/elediardo]

[u/BlitzAtk]

Please more of these explanation pieces. I get confused easily with the more complex JS examples.

[u/elediardo → u/BlitzAtk]

Sure, what complexity would you like explained?

[u/BlitzAtk → u/elediardo]

At this very moment, I am still wrapping my head around the difference between ES5 and ES6, arrow function "=>". I know it an simplified version of something, but it takes me awhile to digest one when I see it.

[u/pookage]

Also, your switch statements can now include blocks:

switch(grade){
    case "A": {
        const message = "Great job!";
        console.log(message);
        break;
    }
    case "B": {
        const message = "OK Job";
        console.log(message);
        break;
    }
    ...etc...
}

whereas without:

switch(grade){
case "A":
    const message = "Great job!";
    console.log(message);
    break;
case "B":
    const message = "OK Job"; // ERROR - const message already declared
    console.log(message);
    break;
...etc...

}

[u/Barnezhilton → u/pookage]

Do you still need the break; if you use brackets?

Seems redundant

[u/pookage → u/Barnezhilton]

I agree, but, alas - still need break.

[u/opticsnake → u/Barnezhilton]

If you don't break, it will execute the block and then still fall through to the default block.
Although, this does feel like a special case for break anyways since the scope it would be breaking on would be the case block and not the whole switch statement...

[u/[deleted] → u/pookage]

Cna you do put an if statement inside ?

[u/pookage → u/[deleted]]

Yup! It's still javascript - you can do whatever you want inside.

[u/lindymad]

In Javascript, can a switch contain multiple cases for one rule? e.g.

switch(grade){
case "A":
case "B":
    console.log("Above Average");
    break;
case "C":
    console.log("Average");
    break;

If so, might be worth mentioning in the example?

[u/Barnezhilton → u/lindymad]

Yeah this is a huge miss for fall through conditions understanding

[u/Barnezhilton → u/[deleted]]

What Lindymad wrote above me about stacking conditions is the example. You can have multiple conditions run the same switch block.

And also if you don't use a break you can fall-through to the next condition/break.

So like:

switch (typ) {
case 'A':
case 'B':
   do_something for A and B;
case 'C':
   do_something for C, but also A and B will fall through because no break;
   break;
default:
}

[u/AmauryH → u/lindymad]

Yes, you can.

[u/iamrbn]

That’s pretty awesome… thx mate +1

[u/[deleted]]

I don't really use switch cases often as I was under the impression that the cases can only be exact values like case 'a': rather than case if (grade>75): and I often end up using multiple if statements. I've often seen advice like ' if you are using more than three if statements it's time to refactor to a switch statement' but I've never been able to do that.

I've just learned of enums in C and I do see switch cases used a lot more there because of it, but unless I'm misunderstanding switch statments it seems less useful in JS than other languages.

[u/Jay_Hogwarts → u/[deleted]]

So I had a scenario like this recently where one of my cases needed to be a conditional. I used a ternary operator to solve it e.g. case (grade > 75 ? grade : null)

[u/[deleted]]

If you're using it inside a function, you can close your switches with return

[u/Tintin_Quarentino]

Switch case is <3... Wonder why hasn't Python done it yet? I know we can do dict & use that as switch case, but official low level implementation would be so much better.