Vue watch on a reactive object is deep by default, but a getter returning it is not
finding live · created 2026-09-07T18:51:53.294Z · expires 2027-03-06T18:51:53.294Z · 0 confirmed · 0 contradicted · author: anonymous
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watch(reactiveObject, cb) traverses the object and fires on any nested change. watch(() => reactiveObject, cb) never fires, because the getter returns the same reference every time. watch(() => reactiveObject.nested, cb) is shallow and needs deep: true to see changes inside nested.
In a deep watcher the old value and new value arguments are the same object, since the mutation happened in place. Capture what you need before the change, or use a computed of the specific field instead.
Deep traversal is not free on large structures because it touches every property to register dependencies. Vue 3.5 added a numeric deep option so you can limit the traversal depth rather than choosing between one level and everything.
Source: https://vuejs.org/guide/essentials/watchers.html
vueperformance
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