Is it considered valid in JavaScript or TypeScript to group values using (value1 || value2) for comparisons, and if it is, what is the reasoning behind

Question

Is it considered valid in JavaScript or TypeScript to group values using (value1 || value2) for comparisons, and if it is, what is the reasoning behind

Does anyone know if using the || operator to group values while comparing a single variable is valid in the most recent versions of JavaScript or TypeScript? If not, what could be preventing this from becoming a valid syntactic sugar feature at some point? And if it is allowed, in which version of JS was this functionality added and what is the name of this type of shortcut comparison?

const exampleVar: 'a' | 'b' | 'c' | 'd' = 'a'

// Checking if exampleVar is 'a' or 'b'
if ( exampleVar === ('a' || 'b') ) {
  console.log('Yay!');
} else {
  console.log("Not 'a' or 'b' - Boo!");
}

I would expect this to return true if exampleVar is 'a' or 'b'. It seems to work in console in modern browsers, so my main questions are where can this be safely used and what is this technique called so I can verify its support on platforms like CanIUse.

javascript typescript syntax comparison comparison-operators

Answer 1

Answer №1

Sorry, but that approach won't give you the desired outcome.

exampleVar === ( 'a' || 'b') actually translates to exampleVar === 'a'

The or operator returns the right-hand value if the left-hand value is falsy.

You might be closer to what you want with something like this:

if(['a', 'b'].includes(exampleVar)) {
  ...
}

Answer 2

Sorry, but that approach won't give you the desired outcome.

exampleVar === ( 'a' || 'b') actually translates to exampleVar === 'a'

The or operator returns the right-hand value if the left-hand value is falsy.

You might be closer to what you want with something like this:

if(['a', 'b'].includes(exampleVar)) {
  ...
}

Answer 3

Answer №2

To implement different outcomes based on a variable, you can utilize the switch statement:

switch(userChoice) {
case 'optionA':
case 'optionB':
  console.log('Great choice!');
  break;
case 'optionC':
  console.log('Another excellent choice!');
  break;
default:
  console.log("Not option A or B or C - Try again!");
}

Answer 4

To implement different outcomes based on a variable, you can utilize the switch statement:

switch(userChoice) {
case 'optionA':
case 'optionB':
  console.log('Great choice!');
  break;
case 'optionC':
  console.log('Another excellent choice!');
  break;
default:
  console.log("Not option A or B or C - Try again!");
}

Is it considered valid in JavaScript or TypeScript to group values using (value1 || value2) for comparisons, and if it is, what is the reasoning behind

Answer №1

Answer №2

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