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Use element.dataset to read and change an element’s data-* attributes in JavaScript. Its keys use camel case, but its values remain strings: convert them yourself when your code needs numbers, booleans, or another type.
What the Dataset API does
HTML lets you add custom attributes such as data-item-id to elements. In JavaScript, HTMLElement.dataset exposes those attributes through a DOMStringMap. The dataset property itself is a read-only reference, but you can change or remove its individual entries to update the corresponding HTML attributes.
The WHATWG HTML Living Standard describes custom data attributes as intended for “custom data, state, annotations, and similar, private to the page or application,” where no more appropriate attribute or element exists. See the HTML Living Standard.
How data-* names map to dataset keys
In markup, custom attributes use lowercase, hyphen-separated names. In JavaScript, a hyphen followed by a lowercase ASCII letter is removed and that letter is capitalized: data-index-number becomes dataset.indexNumber.
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| HTML attribute | JavaScript dataset key |
|---|---|
data-index-number |
dataset.indexNumber |
data-parent |
dataset.parent |
data-user-id |
dataset.userId |
Dot notation works for ordinary camel-case keys. Bracket notation is useful when you prefer to write a key as a string: element.dataset['indexNumber']. For predictable mapping, use conventional lowercase words separated by hyphens; MDN advises avoiding non-alphabetic characters after a hyphen in names intended for dataset access. See MDN’s data-* reference.
Read, update, and remove an attribute
This example reads a value, updates an existing attribute, adds another, and removes it:
<article data-index-number="12314" data-parent="cars"></article>
const article = document.querySelector("article");
const index = Number(article.dataset.indexNumber);
article.dataset.parent = "vehicles";
article.dataset.reviewed = "true";
delete article.dataset.reviewed;Reading article.dataset.indexNumber returns the string "12314"; Number() performs the conversion. Assigning "true" stores the string "true", not a Boolean. Likewise, assigning null stores the string "null". Use delete element.dataset.key to remove the matching data-key attribute.
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Dataset values are strings, not typed data
Every dataset value is a string. Parse or validate values explicitly before using them as numbers, Boolean flags, or other types. For example, Number(element.dataset.count) converts a numeric string, but your code should still account for missing or invalid input. Do not rely on a value such as "false" behaving like the Boolean false.
For details on reflection, conversion, and deletion, see MDN’s HTMLElement.dataset reference.
Find elements using data attributes
Use a CSS attribute selector with querySelector to find one matching element, or querySelectorAll to get all matches:
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const oneItem = document.querySelector('[data-item-id="42"]');
const allItems = document.querySelectorAll('[data-state="open"]');You can also iterate over a collection of elements you already have. Choose based on whether you need one known match, all matching elements, or already hold the relevant nodes; the available documentation does not establish that one approach is faster.
CSS can match data attributes for styling, and attr() can use an attribute value in generated content. These values are still HTML attribute strings, not typed CSS data. See MDN’s guide to using data attributes.
When data attributes are a good fit
Use data-* for small pieces of custom information naturally associated with a particular element—for example, an item identifier or a UI variant that JavaScript or CSS needs to act on. If HTML already provides an appropriate semantic attribute or element, use that instead. For information meant to be shared among independent tools, prefer an established standard or vocabulary over a private convention.
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Data attributes are less suitable for state that already belongs in JavaScript and does not need to live on an element, or for data that is not naturally associated with one. The HTML Standard also advises that a page should remain usable if custom data attributes and related CSS are ignored. Libraries used across different sites should namespace their custom attributes to reduce naming collisions.
Keep user-facing content out of data attributes
Do not use a data attribute as the only place for information people need to see or understand. Assistive technology may not expose attribute values, and search engines may not index them. Put user-facing information in document text or an appropriate semantic element instead. MDN outlines these limits in its data attributes guide.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.dataset or getAttribute and setAttribute?
Both approaches read and write the same string-valued HTML attributes. dataset is concise and uses camel-case keys; attribute methods retain the exact HTML spelling. Neither performs automatic type conversion.
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| Task | dataset | Attribute methods |
|---|---|---|
Read data-item-id |
element.dataset.itemId |
element.getAttribute('data-item-id') |
Set data-item-id |
element.dataset.itemId = value |
element.setAttribute('data-item-id', value) |
Choose whichever spelling makes the code easier to read and maintain. If you need to check whether a key is an own dataset property rather than inherited through the prototype chain, use Object.hasOwn(element.dataset, 'key'); the in operator also checks the prototype chain. MDN documents these property-checking details in its dataset reference.
Browser availability
MDN marks HTMLElement.dataset as widely available and reports support across browsers since July 2015. That summary is not a guarantee for every embedded or unusual browser environment; check current compatibility data when supporting a specific legacy target.
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