Conditionally add object to an array while being declared

Question

I have an array of objects:

  const arr = [
    {
      name: 'John',
      money: 45
    },
    {
      name: 'Lui',
      money: 65
    },
    {
      name: 'Kegan',
      money: 100
    },
    ... isNewUser  ? {
      name: 'Eric',
      money: 90
    } : {}
  ]

I need to conditionally add the object when it is declared not using array.push. I've tried using the && operator but I just got errors.isNewUser is a boolean variable and if true, array should have 4 items, else the array should only have 3 which doesn't include the newUser object

Why do you need to do it during initialisation? What is is the problem you're trying to solve? — VLAZ
– VLAZ, Commented Mar 31, 2021 at 16:55
I have a large codebase that contains arrays like this and I now I need to display data conditionally and adding array.push() after every declaration would cause more ugly code. Im trying to keep it as clean as possible — ousmane784
– ousmane784, Commented Mar 31, 2021 at 16:56
If it can be solved in one line using a spread operator than adding if(isNewUser) {...} every time it is used would be mmuch simpler and less duplication — ousmane784
– ousmane784, Commented Mar 31, 2021 at 16:59

Ajith Gopi · Accepted Answer · 2021-03-31 17:03:32Z

32

You can only spread an array into an array. So simply make your conditional element an array.

var arr = [{
        name: 'John',
        money: 45
    },
    {
        name: 'Lui',
        money: 65
    },
    {
        name: 'Kegan',
        money: 100
    },
    ...isNewUser ? [{
        name: 'Eric',
        money: 90
    }] : []
]

Anyways, array.push still looks like a better option here!

answered Mar 31, 2021 at 17:03

Ajith Gopi

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Comments

Bart Hofland · Accepted Answer · 2021-03-31 17:45:53Z

5

I like Ajith Gopi's answer very much.

I would additionally use some helper functions.

function toArray(obj) {
  if (obj == null) {
    return []
  }
  else if (Array.isArray(obj)) {
    return obj
  }
  else {
    return [obj]
  }
}

function iif(condition, trueObj, falseObj) {
  return condition ? toArray(trueObj) : toArray(falseObj)
}

var arr = [
  {
    name: 'John',
    money: 45
  },
  {
    name: 'Lui',
    money: 65
  },
  {
    name: 'Kegan',
    money: 100
  },
  ...iif(isNewUser, {
    name: 'Eric',
    money: 90
  })
]

edited Mar 31, 2021 at 17:45

answered Mar 31, 2021 at 17:25

Bart Hofland

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Comments

sakshya73 · Accepted Answer · 2021-03-31 17:10:36Z

1

let arr = [
    {
      name: 'John',
      money: 45
    },
    {
      name: 'Lui',
      money: 65
    },
    {
      name: 'Kegan',
      money: 100
    },
   ]
 const newObj = {
      name: 'Eric',
      money: 90
    }

  if(newUser){
   arr = [...arr, newObj];
  }

answered Mar 31, 2021 at 17:10

sakshya73

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Comments

windmaomao · Accepted Answer · 2025-01-30 15:56:42Z

0

I really like this question, and this is what i did in the end.

const iif = (cond, obj) => (cond ? [obj] : []);

To use it,

[    
    ...iif(true, ['new item']),
]

Keep in mind, the new item can be very complex object as well.

answered Jan 30 at 15:56

windmaomao

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Comments

Ardiv Jauhari Bin Johar · Accepted Answer · 2025-04-07 03:25:36Z

Instead of && operator, you can use directly construct the array based on the condition. Please try to like this:

let isNewUser = false;

const arrTest1 = [
      {
        name: 'John',
        money: 45
      },
      {
        name: 'Lui',
        money: 65
      },
      {
        name: 'Kegan',
        money: 100
      },
      ...(isNewUser ? [{
        name: 'Eric',
        money: 90
      }] : [])
    ];
console.log("Test case when isNewUser is false")    
console.log(arrTest1)
console.log("=======================================")
isNewUser = true;

const arrTest2 = [
      {
        name: 'John',
        money: 45
      },
      {
        name: 'Lui',
        money: 65
      },
      {
        name: 'Kegan',
        money: 100
      },
      ...(isNewUser ? [{
        name: 'Eric',
        money: 90
      }] : [])
    ];
    
console.log(arrTest2)

Hope your good luck!

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