如何根据条件在数组中添加对象元素

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.

Answer 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/

Answer 2

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"}] : []
];

Answer 3

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

1. Create a pure function to return a new constant with the new object added to the array
2. 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"}] : []
];