Javascript Arrays inside object

Question

i have a arrays inside object like this for example:

{1: Array(4), 2: Array(4), 3: Array(4)}
1: (4) ["11111", "2020-04-02", "14:07", 1]
2: (4) ["22222", "2020-04-02", "14:07", 2]
3: (4) ["3333333", "2020-04-02", "14:07", 3]
(from console log)

in my code there is a option to add array and delete array . And if I delete the second array for example its will become to this:

{1: Array(4), 3: Array(4)}
1: (4) ["11111", "2020-04-02", "14:07", 1]
3: (4) ["3333333", "2020-04-02", "14:07", 3]
(from console log)

How do I make the third object become to 2 ? Make the object manage from the low to the high THANKS.

Instead of using object use array, the index change will automatically be handled. — Gaurav Singh, Apr 02 '20 at 11:36
@GauravSingh: They already are arrays, see the console.log output where it says `Array(x)` and has `[ ]` square brackets! — CherryDT, Apr 02 '20 at 11:39
the object you are using to store arrays, use array to store arrays instead, like 2d array. — Gaurav Singh, Apr 02 '20 at 14:10

Ankush · Answer 1 · 2020-04-05T11:59:19.453

In the object above, when you delete the second array, only that key is removed and this has no impact on other keys. Because object keys act as an identifier to access the location of value corresponding to that key.

If you want that other keys should reset accoding to order. Please use array of arrays instead of objects having arrays as values.

Array - ordered items with numeral indices Object - unordered items with any valid string or number indices.

If it is required to use object, here's the solution to manually do it -

For the index i that needs to be removed, parse the next indices (numerically greater than i) to take key = key - 1, i.e., decreasing their index key by 1.

// index is treated from 1 to n.
const deleteElement = (delete_index, obj) => {
    const keyCount = Object.keys(obj).length;

    // move all elements with keys > delete_index to previous index
    for(let i=delete_index; i<=keyCount; i++) {
        obj[i] = obj[i+1]
    }
    // delete last element
    delete obj[keyCount]
}

While this code may solve the question, [including an explanation](//meta.stackexchange.com/q/114762) of how and why this solves the problem would really help to improve the quality of your post, and probably result in more up-votes. Remember that you are answering the question for readers in the future, not just the person asking now. Please [edit] your answer to add explanations and give an indication of what limitations and assumptions apply. [From Review](/review/low-quality-posts/25756456) — double-beep, Apr 02 '20 at 20:04

score 0 · Answer 2 · answered Apr 02 '20 at 11:51

If you convert your object to an array-like then you can use array methods with it.

An array-like object basically needs a length property and keys that are positive integers. The length needs to be set to one more than the highest index. So, if you have keys 1, 2, 3 then you need length: 4. Yes, it's a bit misleading since there are only three elements but length is more accurately called "next available index".

At any rate, if you transform your object, then you can use Array#splice and set the target using Function#call. Most array methods are intentionally generic so they can work on anything that's an array-like:

const obj = {
  1: ["foo"],
  2: ["bar"],
  3: ["baz"],
  length: 4
}

//delete starting from index 2 and remove 1 item
Array.prototype.splice.call(obj, 2, 1)

console.log(obj);

Note how the indexes after the deleted one shifted and the length was also adjusted automatically.

If you don't know what the length is currently, you can easily find it:

const obj = {
  1: ["foo"],
  2: ["bar"],
  3: ["baz"]
}


const keys = Object
  .keys(obj)   //get all keys
  .map(Number) //convert to numbers
  .filter(key => Number.isInteger(key) && key >= 0); //leave only positive integers

//find the highest
const highestKey = keys.reduce((a, b) =>  Math.max(a, b), -1);

//set the length to the next possible index
obj.length = highestKey + 1;

//delete starting from index 2 and remove 1 item
Array.prototype.splice.call(obj, 2, 1)

console.log(obj);

score -1 · Answer 3 · answered Apr 02 '20 at 11:42

-1

use splice methodarr.splice(2,1) where first argument is index and second will be number of items to remove from array.

answered Apr 02 '20 at 11:42

aurabliss

84
5

Javascript Arrays inside object

3 Answers3

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