Map on Javascript object values without extra variable?

Question

I'm using the following piece of code (which is working fine)

  const result = {}
  Object.keys(timers).forEach(key => {
    result[key] = hydrate(timers[key])
  })
  return result
}

I'm wondering if this is possible in one method? So without having to fill the result object?

You are missing some code becuase return result should be inside another function. — Maheer Ali
– Maheer Ali, Commented Jul 9, 2019 at 18:24
@epascarello That's what my question is about.. Kindly make an answer. — Miguel Stevens
– Miguel Stevens, Commented Jul 9, 2019 at 18:25
Follow the example? developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — epascarello
– epascarello, Commented Jul 9, 2019 at 18:26
You say “without having to fill the result object”, but why do you have to do this? — evolutionxbox
– evolutionxbox, Commented Jul 9, 2019 at 18:30

Ori Drori · Accepted Answer · 2019-07-09 18:27:43Z

3

Convert to entries with Object.entries(), iterate the entries with Array.map() and hydrate the values, and convert back to an object with Object.fromEntries():

const fn = timers => Object.fromEntries(
  Object.entries(timers).map(([k, v]) => [k, hydrate(v)])
)

edited Jul 9, 2019 at 18:27

answered Jul 9, 2019 at 18:26

Ori Drori

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2 Comments

Heretic Monkey Over a year ago

Note for readers: fromEntries is ECMAScript 2019 and is not supported in all browsers/engines as of this writing (see the support grid at the bottom of the linked doc).

Ori Drori Over a year ago

It actually has pretty decent support now days (all except IE/Edge/Opera), and it's easy to polyfill.

epascarello · Accepted Answer · 2019-07-09 18:33:42Z

1

Just use reduce

var timers = {
  a: 2,
  b: 3,
  c: 4
}
 
const hydrate = x => 2*x

var result = Object.entries(timers).reduce((o, [key, value]) => {
  o[key] = hydrate(value)
  return o
}, {})

console.log(result)

without fat arrow

var timers = {
  a: 2,
  b: 3,
  c: 4
}
 
function hydrate (x) { return 2 * x }

var result = Object.entries(timers).reduce(function(o, entry) {
  o[entry[0]] = hydrate(entry[1])
  return o
}, {})

console.log(result)

answered Jul 9, 2019 at 18:33

epascarello

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