Define native method to sort array based on property in array

Question

Been working with this simple task for a bit now and I just can't seem to figure out what the issue is. I have an array of objects, each object has a SetIndex property and I want to insert objects and maintain the array ordered by the objects Set Indices. I thought this was fairly simple but it does not seem to be working as I had expected.

The native method inserts, but the chunk that checks if the array is empty always seems to evaluate to true, and overwrites index 0 every time and does not execute the splice. I think it is something simple about JS I am missing, but I can't seem to figure it out.

Array.prototype.insertAtIndex = function(item) {
    for (i = 0; i < this.length; i++) {
        if(i+1 > this.length)
        {
            if(this[i].SetIndex <= item.SetIndex && this[i+1].SetIndex  >= item.SetIndex)
            {
                this.splice(i,0,item);
            }
        }
    }
    if(this[0].length == 0);
    {
        this[0] = item;
    }
};

I run the following to test the function

item1 = {SetIndex: 0,name: 'item1'};
item2 = {SetIndex: 1,name: 'item2'};
item3 = {SetIndex: 2, name: 'item3'};
item4 = {SetIndex: 3, name: 'item4'};
item5 = {SetIndex: 4, name: 'item5'};
console.log(item1.SetIndex);
my_array = [];
my_array.insertAtIndex(item2);
console.log(my_array);
my_array.insertAtIndex(item1);
console.log(my_array);
my_array.insertAtIndex(item5);

I have tried using if(this[0] == undefined) as well to check if the array is empty but nothing works as I planned

is there a reason not to just implement a custom sort using the property value? i.e. my_array.sort(function(a, b) { return a.SetIndex - b.SetIndex; }); you can sort it whenever you need to make sure they stay in order this way if you need. — Lbatson
– Lbatson, Commented Oct 7, 2014 at 0:39
Well couldn't figure out why my method wouldn't work, but instead of inserting in order I ended up just using the native Array.sort at the end that compared a.SetIndex and b.SetIndex EDIT: I wrote this at the same time intothev01d answered, that is what I ended up doing. But if anyone knows why the original didn't work it would be appreciated — jankyd
– jankyd, Commented Oct 7, 2014 at 0:40

PM 77-1 · Accepted Answer · 2014-10-07 00:45:40Z

1

You have:

for (i = 0; i < this.length; i++) {
    if(i+1 > this.length)
    {
         // dead code

the maximum of i (inside the loop) is this.length-1. Therefore, (i+1 > this.length) can never be true.

answered Oct 7, 2014 at 0:45

PM 77-1

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