convert to bool if "false" or "true", leave string otherwise

Question

What is the most efficient one-liner (if possible) for:

if (val == "true"){
 value = true;
}
else if (val == "false"){
 value = false;
}
else {
 value = val;
}

val is string.

does it help ? https://stackoverflow.com/questions/263965/how-can-i-convert-a-string-to-boolean-in-javascript — Ali Sattarzadeh, Jan 09 '23 at 11:21

score 1 · Accepted Answer · answered Jan 09 '23 at 11:12

1

Do it in one line with ternary operator :

value = val == "true" ? true : (val == "false" ? false : val);

answered Jan 09 '23 at 11:12

Johan

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2

You sure can, but is it really more clear that OP's initial version? Easier to maintain and read? I'd prefer OP's version. – Ivar Jan 09 '23 at 11:30
He asked for a one line. This is one. And very easy to read and understand – Johan Jan 09 '23 at 13:34

score 0 · Answer 2 · answered Jan 09 '23 at 11:44

0

let val = 'false';

val = {'true': true, 'false': false, [val]:val}[val]

console.log(val)

answered Jan 09 '23 at 11:44

Andrew Parks

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Nina Scholz · Answer 3 · 2023-01-09T17:54:20.853

0

You could take an object with null colalescing with the given string.

const
    bOrS = v => ({ true: true, false: false }[v] ?? v);

console.log(bOrS('true'), typeof bOrS('true'));
console.log(bOrS('false'), typeof bOrS('false'));
console.log(bOrS('foo'), typeof bOrS('foo'));

edited Jan 09 '23 at 17:54

answered Jan 09 '23 at 12:01

Nina Scholz

376,160
25
347
392

score 0 · Answer 4 · answered Jan 09 '23 at 15:58

You can do it with just a && and a ||:

value = val == "true" || val != "false" && val;

but will you still understand it when you read it in a month or two?

const toBool = val => val == "true" || val != "false" && val;

["true", "false", "something", ""].forEach(val => {
  const value = toBool(val);
  console.log({ val, value, type: typeof value });
});

convert to bool if "false" or "true", leave string otherwise

4 Answers4