How to add object element in array based on condition

Question

I have static array constant of objects something similar to below.

export const EMPLOYEES = [
  {
    id: 2,
    name: ‘John’,
  },
  {
    id: 3,
    name: ‘Doe’,
  },
  {
    id: 4,
    name: ‘Bull’,
  },
  {
    id: 5,
    name: ‘Scott’,
  },
];

Now I need to add the last element only based on if some condition is true. Some this like if isAmerican() is true.

Can somebody help me here how to add element based on the condition? Thanks.

You can't modify what the constant points to, but you can push to the array. So do something like: if (isAmerican()) { employees.push({ id: 6, name: 'Timmy' }) } — Carwyn Stephen
– Carwyn Stephen, Commented Oct 11, 2018 at 6:31
Now I need to have the last element only based on if some condition is true. What do you mean by have? Remove? Get? — StudioTime
– StudioTime, Commented Oct 11, 2018 at 6:38
@FrankerZ Sure you can, nothing in const makes the array immutable. — Bergi
– Bergi, Commented Oct 11, 2018 at 6:54

wang · Accepted Answer · 2018-10-11 06:39:08Z

30

You can do it using spread operator:

export const EMPLOYEES = [
    {
        id: 2,
        name: "John",
    },
    {
        id: 3,
        name: "Doe",
    },
    {
        id: 4,
        name: "Bull",
    },
    {
        id: 5,
        name: "Scott",
    },
    ... isAmerican() ? [{ id: 6, name: "Jemmy"}] : []
];

answered Oct 11, 2018 at 6:39

wang

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Comments

Mr.Turtle · Accepted Answer · 2018-10-11 07:16:51Z

You should never modify (or try to modify) a constant. I can see two ways you can do this:

Create a pure function to return a new constant with the new object added to the array
Use a spread operator in the definition of the constant

Option 1: Pure function

function makeNewArray(array, objectToAppend, isAmerican) {
    return isAmerican ? [...array, objectToAppend] : array
}

const EMPLOYEES = [
    {
        id: 2,
        name: "John",
    },
    {
        id: 3,
        name: "Doe",
    },
    {
        id: 4,
        name: "Bull",
    },
    {
        id: 5,
        name: "Scott",
    }
];

const arrayWithAmerican = makeNewArray(EMPLOYEES, { id: 6, name: "American Frank"}, true);
const arrayWithoutAmerican = makeNewArray(EMPLOYEES, { id: 6, name: "Not American Frank"}, false);

console.log(arrayWithAmerican);
console.log(arrayWithoutAmerican);

Option 2: Spread operator

function isAmerican(){
    // generic code here.
    return true;
}

const EMPLOYEES = [
    {
        id: 2,
        name: "John",
    },
    {
        id: 3,
        name: "Doe",
    },
    {
        id: 4,
        name: "Bull",
    },
    {
        id: 5,
        name: "Scott",
    },
    ... isAmerican() ? [{ id: 6, name: "American Frank"}] : []
];

hetious · Accepted Answer · 2018-10-11 06:35:28Z

1

If the condition will be fulfilled, simply push an object to your EMPLOYEES array:

let isAmerican = true;

const EMPLOYEES = [
  {
    id: 2,
    name: "John",
  },
  {
    id: 3,
    name: "Doe",
  },
  {
    id: 4,
    name: "Bull",
  },
  {
    id: 5,
    name: "Scott",
  },
];

if(isAmerican) {
    EMPLOYEES.push({
    id: 6,
    name: "Frank"
  })
}
console.log(EMPLOYEES)

Fiddle: https://jsfiddle.net/rqx35pLz/

answered Oct 11, 2018 at 6:35

hetious

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