CODEWITHSUNDEEP
javascriptarraysfor-loopobject
Agamotto
Agamotto

Reputation: 1

Create objects, EACH with unique ids using for loop

So I'm trying to generate an array that will have multiple objects, one of them with another array. Each object should have its own unique id, but when using for loop, each batch has objects with the same repeated ids. using i variable or even adding random number value seems to be not working. Is this even achievable in javascript?

Test.js

const testFunc = () => {
  let resultArray = []
  let testObj = {}
  let testArray = []

  const rn = () => {
    return ~~(Math.random() * 1000)
  }

  for (let i = 0; i < 3; i++) {
    testObj = { id: rn() }
    testArray.push(testObj)
    testObj = {}
  }

  for (let i = 0; i < 3; i++) {
    resultArray.push(testArray)
  }

  console.log(resultArray)
  return resultArray
}

Expected result:

[
  [
    { id: 859, text: 0 },
    { id: 232, text: 1 },
    { id: 240, text: 2 },
    { id: 638, text: 3 },
    { id: 393, text: 4 }
  ],
  [
    { id: 681, text: 0 },
    { id: 384, text: 1 },
    { id: 413, text: 2 },
    { id: 721, text: 3 },
    { id: 985, text: 4 }
  ],
  [
    { id: 348, text: 0 },
    { id: 911, text: 1 },
    { id: 255, text: 2 },
    { id: 816, text: 3 },
    { id: 797, text: 4 }
  ]
]

Result I get:

[
  [
    { id: 859, text: 0 },
    { id: 232, text: 1 },
    { id: 240, text: 2 },
    { id: 638, text: 3 },
    { id: 393, text: 4 }
  ],
  [
    { id: 859, text: 0 },
    { id: 232, text: 1 },
    { id: 240, text: 2 },
    { id: 638, text: 3 },
    { id: 393, text: 4 }
  ],
  [
    { id: 859, text: 0 },
    { id: 232, text: 1 },
    { id: 240, text: 2 },
    { id: 638, text: 3 },
    { id: 393, text: 4 }
  ]
]

Upvotes: 0

Views: 875

Answers (2)

CertainPerformance
CertainPerformance

Reputation: 370679

You're only ever creating a single sub-array. The line

let testArray = []

only runs once, and you do

resultArray.push(testArray)

3 times - so in the result, all sub-arrays in resultArray refer to the same testArray.

Create a new array explicitly instead, and use a nested loop so that there are 3x3 iterations total:

let resultArray = []
let testObj = {}

const rn = () => {
  return ~~(Math.random() * 1000)
}

for (let i = 0; i < 3; i++) {
  const testArray = []
  for (let i = 0; i < 3; i++) {
    const testObj = {
      id: rn()
    }
    testArray.push(testObj)
  }
  resultArray.push(testArray)
}


console.log(resultArray)

Upvotes: 0

Ori Drori
Ori Drori

Reputation: 191966

You push the testArray thrice to the resultArray. Instead generate testArray in a loop, push it to the resultArray, and add the items:

const testFunc = () => {
  const resultArray = []

  const rn = () => {
    return ~~(Math.random() * 1000)
  }

  for (let i = 0; i < 3; i++) {
    const testArray = []
    resultArray.push(testArray)
    
    for (let i = 0; i < 3; i++) {
      const testObj = { id: rn() }
      testArray.push(testObj)
    }
  }

  return resultArray
}

console.log(testFunc())

Upvotes: 1

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