Cast all object fields to boolean

Question

I want to cast all object fields to boolean.

function parseBooleanObject (obj) {
  const flagKeys = Object.keys(obj)
  return flagKeys.reduce(
    (newFlags, key) => (newFlags[key] = obj[key] === 'true'), {}
  )
}

const obj = { showVideo: 'true', isStudent: 'false' }
const parsedObj = parseBooleanObject(obj)
console.log('parsedObj: ', parsedObj)

But this code returns false instead of parsing fields to boolean

{ showVideo: true, isStudent: false }

`newFlags[key] = obj[key] === 'true'` will return the value of the assignment, which is a boolean. The next time the `reduce` callback is invoked it's going to use *that* value as `newFlags`, so for iteration 2+, `newFlags` is always a boolean and you're assigning `true[key]` or `false[key`] — VLAZ, Mar 16 '20 at 12:11
You can always spread the current object into a new one, and add the additional key: `.reduce((newFlags, key) => ({...newFlags, [key]: obj[key] === 'true'}))` — Nick Parsons, Mar 16 '20 at 12:18
const castToBool = (obj => Object.keys(obj).forEach(x => obj[x] = !!obj[x])); let a = { a: 1, b: 2, c: 0, d: 'a', e: '', f: 'b' }; castToBool(a); console.log(a); — Umair Khan, Mar 16 '20 at 12:23
@UmairKhan that works for truthy/falsy values, but doesn't work for parsing OPs data where the values are `"true"` or `"false"` — Nick Parsons, Mar 16 '20 at 12:25

Code Maniac · Accepted Answer · 2020-03-16T12:14:38.330

3

Assignment operator returns only the current key which gets assigned to newFlags, you need to return whole newFlags back.

Here i have used , operator to return newFlags after assignment.

function parseBooleanObject (obj) {
  const flagKeys = Object.keys(obj)
  return flagKeys.reduce(
    (newFlags, key) => (newFlags[key] = obj[key] === 'true', newFlags), {}
  )
}

const obj = { showVideo: 'true', isStudent: 'false' }
const parsedObj = parseBooleanObject(obj)
console.log('parsedObj: ', parsedObj)

I will personally have them in two separate line in order to keep readability maintained

function parseBooleanObject(obj) {
  const flagKeys = Object.keys(obj)
  return flagKeys.reduce(
    (newFlags, key) => {
    newFlags[key] = obj[key] === 'true'
     return newFlags
    }, {}
  )
}

const obj = {
  showVideo: 'true',
  isStudent: 'false'
}
const parsedObj = parseBooleanObject(obj)
console.log('parsedObj: ', parsedObj)

edited Mar 16 '20 at 12:14

answered Mar 16 '20 at 12:11

Code Maniac

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it's worth noting that this is using the comma operator - `(a, b)` evaluates to `b` and not _returning_ a tuple. – Alnitak Mar 16 '20 at 12:13
just curious, but if you'd actually use the second syntax, why did your first answer only show the comma operator version? ;) – Alnitak Mar 16 '20 at 12:15
@Alnitak sure, but here eventually this is what will happen, since we are using implicit return so eventually it will return `b` – Code Maniac Mar 16 '20 at 12:15
@Alnitak thats was just to keep code as close as possible to OP's code, i always bet on simple code :) – Code Maniac Mar 16 '20 at 12:16

Orelsanpls · Answer 2 · 2020-03-16T12:38:46.090

1

You haven't return the correct value from your Array.reduce.

Same answer as @Code Maniac, different syntax.

function parseBooleanObject(obj) {
  return Object.keys(obj).reduce((tmp, x) => {
    tmp[x] = obj[x] === 'true';
    
    return tmp;
  }, {});
}

const obj = {
  showVideo: 'true',
  isStudent: 'false'
};

const parsedObj = parseBooleanObject(obj);

console.log('parsedObj: ', parsedObj)

edited Mar 16 '20 at 12:38

answered Mar 16 '20 at 12:12

Orelsanpls

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I would like to call it better syntax instead of different syntax :) – Code Maniac Mar 16 '20 at 12:18
@CodeManiac I wouldn't dare :p – Orelsanpls Mar 16 '20 at 12:39

score 0 · Answer 3 · answered Mar 16 '20 at 12:12

you have to return object from the reduce function

   function parseBooleanObject(obj) {
        const flagKeys = Object.keys(obj)
        return flagKeys.reduce(
            (newFlags, key) => {
                (newFlags[key] = obj[key] === 'true');
                return newFlags
            }, {}
        )
    }

    const obj = { showVideo: 'true', isStudent: 'false' }
    const parsedObj = parseBooleanObject(obj)
    console.log('parsedObj: ', parsedObj)

score 0 · Answer 4 · answered Mar 16 '20 at 12:13

different approach with for...in loop

function parseBooleanObject (obj) {
  const parsed = {};
  for (let key in obj) parsed[key] = obj[key] === 'true';
  return parsed;
}

console.log(
  parseBooleanObject(
    { showVideo: 'true', isStudent: 'false' }
  )
);

Cast all object fields to boolean

4 Answers4