Vue 3.5's Vapor Mode is an opt-in compilation strategy that eliminates the Virtual DOM, generating direct DOM manipulation code for improved performance. Combined with improvements to defineModel() and v-bind shorthand, it represents the next evolution of Vue's reactivity system.
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What is the primary goal of Vue 3.5 Vapor Mode?
Vapor Mode is an alternative compilation strategy for Vue that produces direct DOM manipulation code instead of Virtual DOM vnodes. This eliminates VDOM diffing overhead and reduces the Vue runtime shipped to the browser.
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In Vue 3.5, defineModel() in a child component creates a two-way binding. What does it replace?
defineModel() is a compiler macro that automatically declares a modelValue prop and an update:modelValue emit, exposing a writable ref. It replaces the verbose manual pattern required before Vue 3.4.
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Vue 3.5 improved v-bind shorthand syntax. What new shorthand was introduced?
Vue 3.5 introduced a same-name shorthand: when a prop name matches the bound variable name, you can write :id instead of :id='id', similar to JavaScript shorthand property syntax in object literals.
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In Vapor Mode, why can reactive primitives update the DOM without VDOM diffing?
Vapor's compiler analyses the template statically and generates direct DOM update instructions tied to each reactive dependency. When a value changes, only the specific DOM property or text node is updated, with no intermediate VDOM representation to diff.
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A component defined with defineComponent() in Vapor Mode is mixed into a standard VDOM Vue app. What is the compatibility implication?
Vue's Vapor interop layer wraps a Vapor component in a thin VDOM-compatible shim so it can be consumed by non-Vapor parent components. The reverse — using a VDOM component inside a Vapor component — also requires the interop adapter, as Vapor trees do not natively understand vnodes.