current community

your communities

more stack exchange communities

company blog
Stack Exchange Inbox Reputation and Badges
tour help
Stack Overflow is a community of 4.7 million programmers, just like you, helping each other.

Join them; it only takes a minute:

Sign up
Join the Stack Overflow community to:
  1. Ask programming questions
  2. Answer and help your peers
  3. Get recognized for your expertise
up vote -2 down vote favorite

I have an array of objects. It had 3 objects

Print out in console. Array of three objects starting at index 0

I then deleted them one by one using arr.splice(0,1) which I repeated 3 times. I then added a new object to the (what is supposed to be an empty array) and printed out the ENTIRE array in console. Console output after adding object to emptied array

As you can see, it IS the only object in the array, but instead of starting with index 0, it starts with index 3. Also, the indexes for 0,1,2 are not there, they are not "null" or anything like it. their gone. What's going on?

This is the actual code for removal. I invoke it 3 times. 

this.removeSelected = function () {

        //Remove from array
        //I have verified that selFramePos=0 many times. 
        f.splice(selFramePos, 1);
}

This object that I keep in each array slot(Just a bunch of data, nothing special):

  Data = {
        normal : normData,
        imageUrl: selfDefaults.viewport.src,
        topLeftX: norm(cf.paper.width, vpo.cx, vpw),
        topLeftY: norm(cf.paper.width, vpo.cy, vpw),
        width: norm(cf.paper.width, vpo.width, vpw),
        height: norm(cf.paper.width, vpo.height, vpw),
        rotation: selfRotator.getRotation().rotation,
        cropping:
        {
            shape: selfSelector.getSelection().shape,
            tlx: mathUtils.normalize(cf.paper.width, selfSelector.getSelection().left, vpw),
            tly: mathUtils.normalize(cf.paper.width, selfSelector.getSelection().top, vpw),
            w: mathUtils.normalize(cf.paper.width, selfSelector.getSelection().width, vpw),
            h: mathUtils.normalize(cf.paper.width, selfSelector.getSelection().height, vpw),
            color: selfSelector.getSelection().color,
            opacity: selfSelector.getSelection().opacity
        },
        filters: null,
        transition:
{
    type: 'dissolve',
    time: 500
},
        requireUserInput: true
    }

My problem was that I kept creating new array slots with an increasing index number like so:

        var i=0
        function add2Array () {
        arr[i]='something'
        i++
        }

So every time I called the function, it created a 'unique id' of sort instead of working with indexes and positions.

I fixed it by removing i and just using 'push' instead of arbitrarily increasing indexes.

share|improve this question
2  
Please show your actual code, including the data structure you start with and the code you use that modifies it. I'm also not sure what is and isn't an array vs. an object which could be part of your problem. Also not sure if you're using sparse arrays that might be confusing you. – jfriend00 Jan 29 '15 at 0:55
    
Can't reproduce: var arr = [1,2,3]; for(var i=0; i<3; ++i) arr.splice(0,1); arr.push(4); Object.keys(arr); – Oriol Jan 29 '15 at 0:57
    
Works fine in the fiddle. Restarts at 0 when repopulating. And also works fine with the push method fiddle – Mikey Jan 29 '15 at 1:01
1  
Please show us how you "added the new object" to the array. – Bergi Jan 29 '15 at 1:08
    
@Bergi Thank you!!!!! That was my problem. (If you want to write an answer about "make sure you insert objects at position 0 or whatever, I'll mark it as the correct answer") – Michael Seltenreich Jan 29 '15 at 1:10
up vote 0 down vote accepted

then I added a new object to the (what is supposed to be an empty) array

But not incorporating its new length, it seems. Use push to add the item and this will be done automatically.

share|improve this answer
    
Worked for me :) – Michael Seltenreich Jan 29 '15 at 1:16
    
@MichaelSeltenreich - It is not clear to me how this answer provides an answer to your question. I gather from your comments that it made you look in the right place, but this question and answer doesn't appear to offer any utility to the StackOverflow community because question and answer don't seem to go together. – jfriend00 Jan 29 '15 at 1:18
    
You are right. I will add an explanation in my question – Michael Seltenreich Jan 29 '15 at 1:26
up vote 0 down vote

JavaScript does not have arrays the way they are implemented in most other languages.

The docs state:

Arrays are list-like objects whose prototype has methods to perform traversal and mutation operations.

ar[i] notation merely refers to property i of object ar that could be numeric.

The following is perfectly legal in JavaScript:

var ar={};
ar[1] = 1;
ar[3] = 2;

We still call it an array. But it does not have to have contiguous indices. What should be noted, that length property of such array will be 3 (the largest value of its index).

So the most logical way to think about JS arrays as special objects (see the quote from docs above) with numeric properties.

share|improve this answer
    
Is there a simple way to remove gaps? A function that will return your array like this: ar[0] = 1; ar[1] = 2; – Michael Seltenreich Jan 29 '15 at 1:05
    
Without a .length it's not an array :-) Or at least, no array methods would work with it (they assume length=0). – Bergi Jan 29 '15 at 1:06
2  
"length property of such array will be 3". Unless you set the length property to ar or to Object.prototype, there won't be any length property, so ar.length will return undefined. – Oriol Jan 29 '15 at 1:06
    
@Oriol - true. Made a clarification. – PM 77-1 Jan 29 '15 at 1:14

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.