In JavaScript, transform an array by mapping it to another array while applying a negative index offset

Alright, I am in the process of transforming an array into another array by displacing indexes based on arbitrary points from two reference arrays. This operation introduces negative indexes which unfortunately hinders the functionality of the script. Is there a way to enable the second array with negative indexes and have the script still work? Or will I need to seek out an entirely new approach? I have simplified the code below.

var firstArray = {
     field: [ 1, 2, 3, 4, 5],
     referenceIndex : 2
};

var secondArray = {
    referenceIndex: 1,
    offset: 0,
    field : {}
};

// Calculating the offset for secondArray.field.
secondArray.offset = firstArray.referenceIndex - secondArray.referenceIndex;

for (i=0; i < firstArray.field.length; i++){
    alert([i - secondArray.offset, firstArray.field[i]].join(" "));
    secondArray.field[i - secondArray.offset] = firstArray.field[i];  // Handling negative indexing.
}

Answer №1

When it comes to arrays, the strictly defined indices are positive integers. Despite this limitation, an array is also considered an object, allowing it to accept strings as properties. This may seem functional on the surface, but caution should be exercised when relying on the accuracy of Array#length.

var arr = [1,2,3];
arr.length //3
arr[10] = 10;
arr.length //11
arr["blah"] = 100;
arr.length //still 11
arr[-1] = 200;
arr.length //still 11

I'd recommend reading this informative article for further insight -

Answer №2

Negative indices are not supported in most cases, but you could manipulate the index by adding or subtracting a number to make it positive. For instance, if you have indices ranging from -2 to 4, the corresponding array values would be from 0 to 6. Therefore, you can adjust the index by +/- 2 to access the desired value.

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