JS: conditionally adding adding in the middle of an array?

Question

If i have an array of data,

const data = [
   {
     name: "dog",
     age: 11
   }, 
   {
     name: "cat",
     age: 21,
   }
]

I want to add an object in the middle of that if a condition is true:

const shouldAddNewAnimal = true;

const animal = {
   name: "tiger",
   age : 22,
}

How would I write that without an else ?

const data = [
   {
     name: "dog",
     age: 11
   }, 
   foo ? animal : {};
   {
     name: "cat",
     age: 21,
   }
]

above is the only way I can think of writing it but I dont want to insert an empty object in there if the condition is not true.

Nina Scholz · Accepted Answer · 2021-12-16 21:12:59Z

3

You could spread with arrays, one with the wanted object and the other empty.

const
    shouldAddNewAnimal = true,
    animal = { name: "tiger", age: 22 },
    data = [
        { name: "dog", age: 11 },
        ...(shouldAddNewAnimal ? [animal] : []),
        { name: "cat", age: 21 }
    ];

console.log(data);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Dec 16, 2021 at 21:12

answered Dec 16, 2021 at 20:46

Nina Scholz

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Comments

Alex Lomia · Accepted Answer · 2021-12-17 16:21:10Z

1

You can use a spread operator:

const foo = true;
const animal = { name: "mouse", age: 10 };

const data = [
   {
     name: "dog",
     age: 11
   }, 
   ...(foo ? [animal] : []),
   {
     name: "cat",
     age: 21,
   }
]

console.log(data);

This will result in the animal being extracted out of its enclosing array and added to the "outer" array.

In the case of "else" path, spreading the null will result in nothing being added to the "outer" array.

edited Dec 17, 2021 at 16:21

answered Dec 16, 2021 at 20:45

Alex Lomia

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4 Comments

Nina Scholz Over a year ago

please try with null. and try to spread false ...

Alex Lomia Over a year ago

@NinaScholz it throws an error, strangely... I removed that example. Thank for pointing it out!

Nina Scholz Over a year ago

your solution still insert an item, even if null to the array.

Alex Lomia Over a year ago

You are right, my bad. Fixed it

Ran Turner · Accepted Answer · 2021-12-16 20:51:45Z

0

You may achieve this by adding null's and filtering them out like so using filter

const shouldAddNewAnimal = false;
const animal = {
   name: 'parrot',
   age:12
}

let data = [
   {
     name: "dog",
     age: 11
   }, 
   shouldAddNewAnimal ? animal : null,
   {
     name: "cat",
     age: 21
   }
].filter(item => item !== null);

console.log(data);

const shouldAddNewAnimal = true;
    const animal = {
       name: 'parrot',
       age:12
    }

    let data = [
       {
         name: "dog",
         age: 11
       }, 
       shouldAddNewAnimal ? animal : null,
       {
         name: "cat",
         age: 21
       }
    ].filter(item => item !== null);

    console.log(data);

answered Dec 16, 2021 at 20:51

Ran Turner

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