Array build with map returning `undefined` when selecting element attribute [duplicate]

Question

I am trying to create an array with only the attribute data-id of each elements but getting an undefined array. What am I doing wrong ?

The declaration: var list = [...document.querySelectorAll("#selection > tr")].map(el => el["data-id"]);

The elements:

<tbody id="selection">
  {% for form in formset %}
    <tr data-id={{form.instance.id}}>
    </tr>
  {% endfor%}
</tbody>

thank you

Datasets might be more appropriate, e.g. element.dataset[keyname] (or el => el.dataset.id in your case) — Yoshi
– Yoshi, Commented Apr 21, 2020 at 6:39

Cedric Cholley · Accepted Answer · 2020-04-21 06:45:04Z

2

data-* attributes are accessed in JS code using .dataset.* (in your case .dataset.id)

final code should be

var list = [...document.querySelectorAll("#selection > tr")].map(el => el.dataset.id);

check out data-*

answered Apr 21, 2020 at 6:45

Cedric Cholley

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Comments

Beingnin · Accepted Answer · 2020-04-21 06:35:10Z

1

var list = [...document.querySelectorAll("#selection > tr")].map(el => el.getAttribute("data-id"));

answered Apr 21, 2020 at 6:35

Beingnin

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