solidjs/solid-docs
[Content]: Document the lack of reactivity when mutating objects or arrays returned by `createSignal`
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#1,621 opened on Aug 11, 2026
good first issuesolid
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Description
📚 Subject area/topic
src/routes/(0)concepts/(2)signals.mdx
📋 Page(s) affected (or suggested, for new content)
/concepts/signals
📋 Description of content that is out-of-date or incorrect
If you create pass an array/object to createSignal, any changes to the underlying object won't be tracked by the reactivity system. Example:
const [arraySig, setArraySig] = createSignal([1, 2, 3]);
const copy = arraySig();
copy.push(...copy.slice(-3).map(x => x + 3));
console.log(arraySig()); /* `arraySig()` is now [1, 2, 3, 4, 5, 6], but UI won't update and effects won't rerun */
I believe this behaviour has to be documented.
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