JavaScript Reactjs state initialize an array of values react usestate initialize with function,react usestate initialize,reactjs state

I am trying to initialize an array of boolean values, where there is a different value on a specific position in array.

If I initialize state like this, empty is array.

state = {
    activeItems: [...new Array(5)].map((item, idx) =>
      idx === 1 ? true : false
    )
}
Answer:1

You will have to first fill your array before mapping it :

state = {
    activeItems: new Array(5).fill().map((item, idx) => idx === 1)
}

const result = new Array(5).fill().map((item, idx) => idx === 1)
console.log(result)
Answer:2

Array from gives you array with <empty slots>

Problem is because map do not iterate over empty spaces

let arr = new Array(5)

let modified = arr.map((e,i)=> console.log(i)) // prints nothing
console.log('modifed prints nothing')
Answer:3

I'm not sure why you mentioned your code returns empty array. Because, it does return the expected output.

You can use Array.from instead to avoid any inconsistency you currently have:

const state = {
    activeItems: Array.from({length:5}, (_, idx) => idx === 1)
}

console.log(state)
Answer:4

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