Adding data to array js, when array is empty, data to n position

Question

Good morning, I am trying to append a value to an empty array declared in a global scope. This array will holds the values of enums results, placed in the same position given by an index, something like this:

array[index] += result

So when the array is empty and I assign that way give me this in chrome console:

(2) [empty, NaN]

Then if I store that result as global variable and copy paste here it gives us this:

[
  null,
  null
]

What I was trying before was something like this:

 if (array[index] == undefined) {
            //first try
            array[index] += result;
            //if 'empty'(better null?) put 0 for now
            array.forEach(x => x == "empty" ? x = 0 : x = result)
            //second try
            array.splice(index, index(plus 1?), result);
}

Because what I want is something like this:

"With a empt array append data in n-position leaving (positions < n-position) with value = 0"

What do you think about this?

Thank you very much,

qiqke

An empty slot is literally that - it's empty. It's doesn't have any value assigned to it, not the string "empty", not null which is a value, nor even undefined which is also a value. An array that contains empty slots is called a sparse array. Using .forEach or any of the other array iteration methods will not go over the empty slots, only filled ones. — VLAZ
– VLAZ, Commented Apr 3, 2020 at 11:47
You should simply check if the slot you're trying to add to is filled and if not, then fill it: if (!array[index]) { array[index] = 0; } array[index] += result. If you know what indexes you need, you could just generate an array filled with zeroes to begin with. — VLAZ
– VLAZ, Commented Apr 3, 2020 at 11:49
Yes, that was what I need, something like that, I didnt think of starting by the negation, also knowing the index yes I can create an array with that lenght, I prefer first option thank you very much!! — Qiqke
– Qiqke, Commented Apr 3, 2020 at 11:52

Waleed Nasir · Accepted Answer · 2020-04-03 12:00:41Z

1

hope its will work

//here is new Array N terms

    var newArray = Array.apply(null,Array(25)).map(a=>null) 

    //newArray[index] = append value

    newArray[2] = 'Hello_1'
    newArray[5] = 'Hello_2'
    newArray[7] = 'Hello_3'
    newArray[11] = 'Hello_4'

    console.log('Append',newArray,'or other show null')

answered Apr 3, 2020 at 12:00

Waleed Nasir

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3 Comments

Qiqke Over a year ago

I'm gonna check in a few hours, looks really nice, thank you (:. I'll let you know later!

Qiqke Over a year ago

Sorry for the delay @walled-naser . Your answer fits well with what I needed, so thank you so much, could you please provide some text to explain what did you do?? :) . I have marked as the right one.

Waleed Nasir Over a year ago

Hi also sorry for the delay, here is my answer, i created new Array which length is 25 and value is empty so then i place map ".map(a=>null)" and replace empty to null, thats allow to assign any value to specific index,

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