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Javascript Switch case statement : fall-through all cases when expression is 'all'

How can I implement this behavior in JavaScript Switch Statements

expression = 'all' or '1' or '2' 

switch (expression)
{
   case "all" : print case 1 and case 2 
      
   case "1" : print only case 1 

   case "2" print only case 2
}

How can I do that? If there’s no way to do something like that in JavaScript, I want to know an alternative solution.

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5

Answers


  1. 0

    You should read this first: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/switch

    let text = "all" // this could be '1' or '2';

switch (text) {
  case '1':
    console.log('print case 1');
    break;
  case '2'
    console.log('print case 2');
    break;
  default:
    console.log('print case 1 and 2');
}

    This is essentially how you would handle that in Javascript.
    Now, if you want types that is another conversation.

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  2. 0

    Maybe a ‘mapping’ object would fit your needs.

    Check the key on the object, call that case if needed.

    On all, loop over Object.values(obj) to call all the cases

    const mapper = {
  "1": () => console.info('Do case 1'),
  "2": () => console.info('Do case 2')
}

const test = (i) => {
    if (i === 'all') {
        Object.values(mapper).forEach(c => c());
    } else {
        if (mapper[i]) mapper[i]();
        else console.error('No case for', i);
    } 
}

test("1");
test("2");
test("all");
test("9");
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  3. 0

    You can use the switch statements like this:

    expression = 'all'  // "1" or "2"

switch (expression) {
   case "all":
      console.log("1")
      console.log("2")
      break;

   case "1":
      console.log("1");
      break;

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

   default:
      console.log("Default case");
}

    Please note that a block will execute until a break statement is encountered. If you do not use the break statement, the execution will fall through. For example, this statement will print 1, 2, and then 1 again because we are not using the break statement in the first case:

    expression = ‘all’ // "1" or "2"

    switch (expression) {
   case "all":
      console.log("1");
      console.log("2");

   case "1":
      console.log("1");
      break;

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

   default:
      console.log("Default case");
}
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  4. 0

    You can construct your own "switch" kind of

    const betterSwitch = value => cases => {
  if (value === 'all') {
    Object.values(cases).forEach(Reflect.apply)
  } else {
    cases[value]()
  }
}

const expression = 'all'
betterSwitch(expression)({
  '1': () => {
    console.log('1')
  },
  '2': () => {
    console.log('2')
  }
})

    Or you can use a reverse switch trickery

    const expression = 'all'

const allOr = v => ['all', v].includes(expression)

switch (true) {
  case allOr('1'):
    console.log('1')
    break
  case allOr('2'):
    console.log('2')
    break
}
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  5. 0

    You could take two condition instead.

    function fn(expression) {
   if (expression === '1' || expression === 'all') console.log(1);
   if (expression === '2' || expression === 'all') console.log(2);
}

fn('1');
console.log('----------');
fn('2');
console.log('----------');
fn('all');
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