set_attribute() — svelte Function Reference

Source Code

packages/svelte/src/internal/client/dom/elements/attributes.js lines 162–200

export function set_attribute(element, attribute, value, skip_warning) {
	var attributes = get_attributes(element);

	if (hydrating) {
		attributes[attribute] = element.getAttribute(attribute);

		if (
			attribute === 'src' ||
			attribute === 'srcset' ||
			(attribute === 'href' && element.nodeName === 'LINK')
		) {
			if (!skip_warning) {
				check_src_in_dev_hydration(element, attribute, value ?? '');
			}

			// If we reset these attributes, they would result in another network request, which we want to avoid.
			// We assume they are the same between client and server as checking if they are equal is expensive
			// (we can't just compare the strings as they can be different between client and server but result in the
			// same url, so we would need to create hidden anchor elements to compare them)
			return;
		}
	}

	if (attributes[attribute] === (attributes[attribute] = value)) return;

	if (attribute === 'loading') {
		// @ts-expect-error
		element[LOADING_ATTR_SYMBOL] = value;
	}

	if (value == null) {
		element.removeAttribute(attribute);
	} else if (typeof value !== 'string' && get_setters(element).includes(attribute)) {
		// @ts-ignore
		element[attribute] = value;
	} else {
		element.setAttribute(attribute, value);
	}
}