Creating arrays with ID numbers as keys leads to the generation of numerous other arrays, each with keys less than the specified number

Question

Creating arrays with ID numbers as keys leads to the generation of numerous other arrays, each with keys less than the specified number

I need to categorize an array based on a specific number (idGroup variable - integer) which is 3355 in this scenario. Below is the code I am using:

if (sortedReservationsByGroup['grouped'] === undefined) {
            sortedReservationsByGroup['grouped'] = new Array();
          }
          if (sortedReservationsByGroup['grouped'][idGroup] === undefined) {
            sortedReservationsByGroup['grouped'][idGroup] = new Array();
          }

          sortedReservationsByGroup['grouped'][idGroup].push(item);
        }

This is how JavaScript executes it:

https://i.sstatic.net/FFrKE.png

javascript

Answer 1

Answer №1

It is recommended to use an object as a default value instead of an array.

sortedReservationsByGroup['group'] = sortedReservationsByGroup['group'] || {};

When using an array, you may encounter a sparse array with empty holes inside, as adding elements with greater indices increases the length of the array, leaving some slots undefined if not previously filled.

var array = [],
    object = {};

array[5] = 42;
object[5] = 42;

console.log(array); // sparse array with undefined
console.log(object);

Answer 2

It is recommended to use an object as a default value instead of an array.

sortedReservationsByGroup['group'] = sortedReservationsByGroup['group'] || {};

When using an array, you may encounter a sparse array with empty holes inside, as adding elements with greater indices increases the length of the array, leaving some slots undefined if not previously filled.

var array = [],
    object = {};

array[5] = 42;
object[5] = 42;

console.log(array); // sparse array with undefined
console.log(object);

Creating arrays with ID numbers as keys leads to the generation of numerous other arrays, each with keys less than the specified number

Answer №1

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