Mapping an array inside a loop

Question

I need to assign an object inside a loop. Here's my code :


let dataObj = {}
let dataArr = []
 ,    temp = []

while ( i < file.length ) {
  array[i].forEach(item => temp.push(item))

  dataObj.name = temp[0]
  dataObj.nim = temp[1]

  dataArr.push(dataObj)

  temp = []
  i++
}

Expected output:

// dataArr = [{name: panji, nim: 123}, {name: gifary, nim: 234}]

Reality :

// dataArr = [{name: gifary, nim: 234}, {name: gifary, nim: 234}]

I'm not sure how can I do this right. Does anybody know the way?

Thank you for your help!

You are not mapping an array. You are just misusing .map instead of something more appropriate like .forEach. — VLAZ
– VLAZ, Commented Aug 3, 2019 at 11:32
Well, what's your input? The output being wrong doesn't make sense unless we know what data you operate on. It might be that you are doing this in reverse and you might need to iterate backwards or unshift instead of push — VLAZ
– VLAZ, Commented Aug 3, 2019 at 11:37

Anurag Srivastava · Accepted Answer · 2019-08-03 11:36:47Z

2

dataObj is a reference to the same object. You can do it without using a variable:

  dataArr.push({
     name: temp[0],
     nim : temp[1]
  })

answered Aug 3, 2019 at 11:36

Anurag Srivastava

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Anurag Srivastava Over a year ago

Glad to help, most probable reason would be a lack of information in the question, such as what is the input. So any answers would be considered guesswork till the question is more complete.

William Gunawan · Accepted Answer · 2019-08-03 11:38:18Z

0

You are facing reference problem. Object set by reference will cause same data when you push to array because its same object with different variable name

while ( i < file.length ) {
  array[i].forEach(item => temp.push(item))
  // use new object instead
  let dataObj = {name: temp[0], nim: temp[1]};

  dataArr.push(dataObj)

  temp = []
  i++
}

Create new object instead or clone your object using this

let newObj = JSON.parse(JSON.stringify(dataObj);

answered Aug 3, 2019 at 11:38

William Gunawan

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