javascript: switch statement

Question

I'm trying to learn how to do a switch statement using javascript. Can you guys help me how to convert this one into switch statement?

        if (x == ix && y == iy){//should be the default 
            x.style.backgroundColor = 'white'; 
        }
        if(x < ix){
            x.style.backgroundColor = 'red'; 
        }
        else if(x > ix){
            x.style.backgroundColor = 'blue';  
        }
        if(y < iy){
            x.style.backgroundColor = 'green'; 
        }
        else if(y > iy){
            x.style.backgroundColor = 'yellow';  
        }

I wouldn't rewrite this using a switch statement, and it isn't really possible either. By the way if x == ix but y != iy then you may have a case which sort of falls through the cracks. You should double check your logic. — Tim Biegeleisen
– Tim Biegeleisen, Commented Nov 18, 2017 at 7:21
have you made a little graphic about the result? the values of y have a higher priority over x. — Nina Scholz
– Nina Scholz, Commented Nov 18, 2017 at 8:45

frick · Accepted Answer · 2017-11-18 07:24:59Z

1

JavaScript does not support operations other than strict equality in switches. In other words, you cannot write that program as a switch.

In a switch, you can compare a variable to different values (or cases) and check if they are equal. If they are, you execute the code given under the case.

There is a drawback, however, and it is that you can convert this code into a switch easily:

if (a === 1) {
  console.log("one");
} else if (a === 2) {
  console.log("two");
} else {
  console.log("Out of range! :(");
}

The above code in switch is

switch (a) {
  case 1:
    console.log("one");
    break;

  case 2:
    console.log("two");
    break;

  default:
    console.log("Out of range! :(");
    break;
}

But you cannot do the same to a code that contains relational operations.

switch (a) {
  case > 1: // throws error
    doSomething();
    break;
}

edited Nov 18, 2017 at 7:24

answered Nov 18, 2017 at 7:19

frick

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4 Comments

Derek 朕會功夫 Over a year ago

Well... here's something that you might find surprising jsfiddle.net/DerekL/jpw147pr

Lutianna Over a year ago

I see i came from php backend just trying if javascript can do such a php

frick Over a year ago

@Derek朕會功夫, that's interesting, but unfortunately, that's not what I mean here.

Derek 朕會功夫 Over a year ago

@KarthaCoder I get your point and I was just sharing an interesting piece of code ;) I'm actually not sure whether it should be used in production.

Radhe Sham · Accepted Answer · 2017-11-18 07:22:00Z

0

Hope this could be helpful to convert your above conditions.

switch (new Date().getDay()) {
    case 0:
        day = "Sunday";
        break;
    case 1:
        day = "Monday";
        break;
    case 2:
        day = "Tuesday";
        break;
    case 3:
        day = "Wednesday";
        break;
    case 4:
        day = "Thursday";
        break;
    case 5:
        day = "Friday";
        break;
    case 6:
        day = "Saturday";
}

answered Nov 18, 2017 at 7:22

Radhe Sham

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