Get all id from Javascript objects [duplicate]

Question

I have following object structure, and

[
  { id: 183, firstName: 'first0', lastName: 'last0', std: 0 },
  { id: 184, firstName: 'first1', lastName: 'last1', std: 1 },
  { id: 185, firstName: 'first2', lastName: 'last2', std: 2 }
]

I want to iterate through the object and get [183,184,185]. Here is what I have tried

alreadyCachedData = [
  { id: 183, firstName: 'first0', lastName: 'last0', std: 0 },
  { id: 184, firstName: 'first1', lastName: 'last1', std: 1 },
  { id: 185, firstName: 'first2', lastName: 'last2', std: 2 }
]
for (var key in alreadyCachedData[0]) {
  if (alreadyCachedData[0].hasOwnProperty(key)  == "id") {
    var val = alreadyCachedData[0][key];
    console.log(val);
  }
}

But I don't get required result, any help?

alreadyCachedData[0].hasOwnProperty(key) == "id" will never be true, hasOwnProperty returns a boolean. Neither true nor false is ever == "id". — T.J. Crowder
– T.J. Crowder, Commented Jan 26, 2022 at 18:19
What is alreadyCachedData? What does alreadyCachedData[0].hasOwnProperty(key) return? — mykaf
– mykaf, Commented Jan 26, 2022 at 18:20

Micael Levi · Accepted Answer · 2022-01-26 18:23:40Z

5

it's easy with Array.map

const out = alreadyCachedData.map(o => o.id)

answered Jan 26, 2022 at 18:23

Micael Levi

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