Uncaught TypeError: Cannot set property '0' of undefined

Question

I keep getting Uncaught TypeError: Cannot set property '0' of undefined, but I can't for my life figure out what is wrong!

var anchor = [];
getAnchors();
function getAnchors() {
    $('.anchor').each(function(i) {
        anchor[i] = $(this).offset().left;
    });
}

So what is wrong with this code snippet? I have declared anchor as an array. I've been checking for silly typos for an hour now. The error lies in i. But what is the error?

Edit: I found out what's wrong.

1st problem I notice is that you're assigning non indexed keys to the array. Did you mean `anchor[i] = {}`? — elclanrs, Jun 20 '13 at 07:00
An array doesn't have keys like that, you're looking for an object — adeneo, Jun 20 '13 at 07:01

score 1 · Answer 1 · answered Jun 20 '13 at 07:00

1

Try returning the array instead? Like this:

function getAnchors() {
    var allAnchors = [];
    $('.anchor').each(function(i) {
        allAnchors.push($(this).offset().left);
    });
    return allAnchors;
}

var anchor = getAnchors();

answered Jun 20 '13 at 07:00

Kristoffer K

2,053
18
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score 1 · Answer 2 · answered Jun 20 '13 at 07:01

You need to create the object property before you assign a value to it.

    var anchor = [];
    $('.anchor').each(function(i) {
        anchor[i] = [{
            pos: null,
            id: null
        }];
        anchor[i]['pos'] = $(this).offset().left;
        anchor[i]['id'] = $(this).attr('id');
    });

then make the assignment and overwrite null with your values.

score 1 · Accepted Answer · answered Jun 20 '13 at 07:03

1

You can use $.map to build arrays :

var anchor;
function getAnchors() {
    anchor = $.map($('.anchor'), function(el) { return $(el).offset().left; });
}

answered Jun 20 '13 at 07:03

adeneo

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score 1 · Answer 4 · answered Jun 20 '13 at 07:08

1

I found the answer. I just had to declare anchor in the function instead.

getAnchors();
function getAnchors() {
    var anchor = [];
    $('.anchor').each(function(i) {
        anchor[i] = $(this).offset().left;
    });
    // perhaps sort anchor
    console.log(anchor);
}

Thanks for the replies though.

answered Jun 20 '13 at 07:08

AKG

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There's no point on doing that TBH. Check @adaneo's answer if that's what you need. – elclanrs Jun 20 '13 at 07:13

score 0 · Answer 5 · answered Jun 20 '13 at 07:03

0

You can do this:

var anchors = $('.anchor').map(function() {
  return {
    pos: $(this).offset().left,
    id: this.id
  }
}).get();

answered Jun 20 '13 at 07:03

elclanrs

92,861
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Uncaught TypeError: Cannot set property '0' of undefined

5 Answers5